Updated

Hurricane Katrina (search) pounded the Gulf Coast Monday with heavy winds and sheets of rain, slamming Mississippi, Louisiana, Alabama and the Florida Panhandle.

As entire neighborhoods in New Orleans were submerged in water, Katrina sent boats hurling onto land in Mississippi and sent water pouring into the state's beachfront casinos.

Two deaths related to Katrina were reported late Monday in southwest Alabama — and three in central Mississippi.

In Alabama, Washington County EMA Director Debora Nichols said one vehicle hydroplaned on a highway during heavy rains from the storm and struck another, killing one person in each vehicle.

Mississippi emergency officials confirmed late Monday that the three deaths there were in Warren, Hinds and Leake counties — more than 150 miles north of the coast. Few details were immediately available.

President Bush declared Louisiana and Mississippi major disaster areas, making them eligible for federal aid to help in recovery and cleanup efforts.

The gigantic storm, which by late morning had weakened from a Category 4 to a Category 3, with 145-mph winds, centered itself east of New Orleans, sparing the city its full fury, barreling inland along the Louisiana-Mississippi state line. At 3 p.m. EDT, Katrina was centered about 20 miles southwest of Hattiesburg, Miss., moving northward at about 19 mph. Its winds had dropped to about 95 mph, making it a Category 1 storm.

But the Big Easy was still pummeled. After the storm had passed, mangled street signs, crumbled brick walls in the French Quarter, fallen trees on streetcar tracks and highrises with almost all of their windows blown out could be seen. White curtains that were sucked out of the shattered windows of a hotel became tangled in treetops.

An estimated 40,000 homes flooded in St. Bernard Parish just east of New Orleans.

At 5 p.m. EDT, Katrina was about 30 miles northwest of Laurel, Miss., and moving north at 18 mph. It was a weak Category 1 hurricane with maximum gusts near 75 mph. Forecasters said the storm may spawn tornadoes over parts of Alabama, Georgia and the Florida Panhandle.

In the Louisiana Superdome, 8,000 to 9,000 poor and elderly residents who had taken shelter inside the massive football stadium looked up to see parts of the roof torn off.

Click here to track Hurricane Katrina

National Hurricane Center Director Max Mayfield warned that New Orleans would be continue to slammed through Monday by the slow-moving storm, and that Katrina's potential 15-foot storm surge, down from a feared 28 feet, was still substantial enough to cause extensive flooding.

"I'm not doing too good right now," Chris Robinson said via cellphone from his home east of the city's downtown. "The water's rising pretty fast. I got a hammer and an ax and a crowbar, but I'm holding off on breaking through the roof until the last minute. Tell someone to come get me please. I want to live."

Bush, urging prayer for Gulf Coast communities "hit hard" by Katrina, weighed whether to release oil from petroleum reserves to help refiners, administration officials said.

"I want the folks there on our Gulf Coast to know that the federal government is prepared to help you when the storm passes," Bush said during a speech in Arizona, urging people to "pray for the health and the safety of all our citizens."

More than 5,000 National Guard troops were activated in four states to assist with recovery operations along the Gulf Coast.

Ed Rappaport, deputy director of the hurricane center, estimated that the highest winds in New Orleans were about 100 mph. Louisiana Gov. Kathleen Blanco said her office had reports of as many 20 building collapses in New Orleans, and scores of residents stranded in attics or on rooftops

On the south shore of Lake Ponchartrain, ywo people were stranded on the roof as murky water lapped at the gutters.

"Get us a boat!" a man in a black slicker shouted over the howling winds.

Across the street, a woman leaned from the second-story window of a brick home and shouted for assistance.

"There are three kids in here," the woman said. "Can you help us?"

At least a half-million people were without power from Louisiana to Florida's Panhandle, including 370,000 in southeastern Louisiana and well over 100,000 each in Alabama and Mississippi.

Katrina recorded a storm surge of more than 20 feet in Mississippi, where windows of a major hospital were blown out and billboards were ripped to shreds. In some areas, authorities pulled stranded homeowners from roofs or rescued them from attics. In Alabama, exploding transformers lit up the early morning sky and muddy, 6-foot waves engulfed stately, million-dollar homes along Mobile Bay's normally tranquil waterfront.

Katrina, which a day before had grown to a 175-mph, Category 5 behemoth — the most powerful level on the scale — made turned east and made landfall about 6:10 a.m. CDT east of Grand Isle (search) in the bayou town of Buras.

The storm's winds dropped to 125 mph as it pushed inland, threatening the Gulf Coast and the Tennessee Valley with as much as 15 inches of rain over the next couple of days, and up to 8 inches in the drought-stricken Ohio Valley and eastern Great Lakes.

Emergency officials had not been able to reach some of the hardest-hit areas to determine the number of injuries or deaths. Officials across the region sent water rescue teams out and stood ready to dispense ice, water and meals to hurricane-stricken residents.

In the Big Easy: 'God's Got Our Back'

In New Orleans, the storm shattered scores of windows in high-rise office buildings and on five floors of the Charity Hospital, forcing patients to be moved to lower levels. At the Windsor Court Hotel, guests were told to go into the interior hallways with blankets and pillows and to keep the doors to the rooms closed to avoid flying glass.

In suburban Jefferson Parish, Sheriff Harry Lee said residents of a building on the west bank of the Mississippi River called 911 to say the building had collapsed and people might be trapped. He said deputies were not immediately able to check out the building because their vehicles were unable to reach the scene.

Police were already tracking down looters.

New Orleans' historic French Quarter appeared to have escaped the catastrophic flooding that forecasters had predicted although some parishes were reportedly under six feet of water.

On Jackson Square, two massive oak trees outside the 278-year-old St. Louis Cathedral came out by the roots At the hotel Le Richelieu, 73-year-old Josephine Elow of New Orleans pressed her weight against the broken French doors of her room as a hotel employee tried to secure them.

"It's not life-threatening," Elow said as rain water dripped from her face. "God's got our back."

For years, forecasters have warned of the nightmare scenario a big storm could bring to New Orleans, a bowl of a city that is up to 10 feet below sea level in spots and relies on a network of levees, canals and pumps to keep dry from the Mississippi River on one side, Lake Pontchartrain on the other.

The fear was that flooding could overrun the levees and turn New Orleans into a toxic lake filled with chemicals and petroleum from refineries, as well as waste from ruined septic systems.

Officials said a levee broke on one canal, but did not appear to cause major problems.

Blanco took little comfort in the fact that the hurricane may have spared New Orleans much worse flooding, given the still uncertain toll in surrounding parishes.

"I can't say that I feel that sense that we've escaped the worst," she said. "I think we don't know what the worst is right now."

"The pumps are still working up there but can't keep up with the water coming in," Rep. Charlie Melancon, D-La., told FOX News, noting that there has been extensive wind and water damage to the city.

"It's going to be difficult … some people are already trying to get back onto the city and the hurricane-force winds have not subsided yet. We're trying to get the message out to them: 'Just stay away,'" he said.

New Orleans Mayor Ray Nagin had ordered a mandatory evacuation over the weekend for the 480,000 residents of the vulnerable city; he estimated about 80 percent heeded the call.

About 3,600 members of the Louisiana National Guard were assisting state police with the evacuation of New Orleans and helped establish 122 shelters across the state.

"We're doing it all," said Louisiana Guard spokesman Lt. Col. Pete Snyder.

Snyder predicted that the shelters in Louisiana will have enough water, cots and Meals Ready to Eat for those forced from their homes by the storm. Guard troops are providing security and screening for New Orleans residents seeking shelter at the Superdome. The Louisiana Guard was also standing by with helicopter support, if necessary.

The Army Corps of Engineers is anticipating requests to pump water out of New Orleans and has teams ready to move into impacted areas with necessary support like ice, water, temporary power, housing and roofing, and debris removal.

Dan Packer, CEO of Entergy New Orleans, Inc., which provides power for southeast Louisiana, said Katrina has inflicted the most extensive damage to that region's power grid in its history. Packer says 750,000 southeast Louisiana customers are without power and full restoration will take at least a month.

New Orleans has not taken a direct hit from a hurricane since Betsy in 1965, when an 8- to 10-foot storm surge submerged parts of the city in seven feet of water. Betsy, a Category 3 storm, was blamed for 74 deaths in Louisiana, Mississippi and Florida.

Katrina hit the southern tip of Florida as a much weaker storm Thursday and was blamed for 11 deaths. The storm, the sixth hurricane to hit Florida in the past year, knocked out power to 1.45 million customers.

A 'Devastating Hit' in Mississippi, Alabama

In Alabama's Mobile Bay, Fred Wright's whole yard was flooded and muddy waves were hitting the back of his home. Wright, shirtless and wearing shorts, spoke of the high-dollar real estate on the waterfront: "There are lots of homes through here worth a million dollars. At least they were yesterday."

By midday, the brunt of the storm had moved beyond New Orleans to Mississippi's coast, home to the state's floating casinos, where Katrina washed sailboats onto a coastal four-lane highway. The Beau Rivage Hotel and Casino, one of the premier gambling spots in Biloxi, had water on the first floor, and the governor said other casinos were flooded as well.

Katrina recorded a storm surge of at least 20 feet in some parts, where windows of a major hospital were blown out, utility poles dangled in the wind, and casinos were flooded. In some areas, authorities pulled stranded homeowners from roofs or rescued them from attics. In Alabama, exploding transformers lit up the early morning sky as power outages spread.

Katrina was the most powerful storm to affect Mississippi since Hurricane Camille (search) came in as a Category 5 in 1969, killing 143 people along the Gulf Coast.

"Let me tell you something folks. I've been out there. It's complete devastation," said Gulfport, Miss., Fire Chief Pat Sullivan, who ventured into the hurricane to check threatened areas. "What you're looking at is Camille II."

Mississippi activated 853 National Guard troops to help with debris removal, security and logisitical support.

Gov. Haley Barbour said the most immediate concern now was search and rescue. He said unprecedented storm surges were hitting his state and many places along the coast were underwater. Some people were trapped in their homes and other buildings but rescue crews are unable to work until the winds die down. He also urged people not to return to their homes, as downed power lines and other perils still abound.

Barbour also warned that looters who may take advantage of the situation will be treated "ruthlessly."

"Looting will not be tolerated, period, and rules of engeagement will be as aggressive as the law allows," Barbour said during a press conference. "Security goes hand-in-hand with search and rescue."

In Alabama, Police Chief Arthur Bourne said the water was as high as it was during Hurricane Ivan (search) a year ago, meaning it could be days before homeowners get in to assess damage and begin cleaning up.

"They need to just stay put. We'll let them know when they can get back in," Bourne said.

Crude oil futures spiked to more than $70 a barrel in Singapore for the first time Monday as Katrina targeted an area crucial to the country's energy infrastructure, but the price had slipped back to $68.95 by midday in Europe. The storm already forced the shutdown of an estimated 1 million barrels of refining capacity.

Administration officials said Bush seemed likely to authorize a loan of some oil from the Strategic Petroleum Reserve (search). But details remained in flux and no decision was imminent, they said.

Energy Secretary Samuel Bodman said in a statement that the SPR can be used in case of a natural disaster and that officials have been in contact with SPR site managers and oil refineries to prepare for any disruption in oil production.

"Over the next few days, we will continue to gain more information on the specific needs and then be able to make a better determination on how we can help," Bodman said.

The Associated Press contributed to this report.