The international airport in St. Louis closed indefinitely Saturday after a tornado swept through a terminal, injuring several people.

Lambert-St. Louis International Airport said in a statement Saturday that it will remain closed pending the return of electric power but is working to resume up to 70 percent of airline service by Sunday if power can be returned to Airport facilities. 

The airport's busiest terminal sustained heavy damage from fierce winds that blew out a majority of windows and sections of the concourse roof, Lambert-St. Louis International Airport spokesman Jeff Lea said.

Still, Lea said once sustained power is returned, the airport is confident it can support the return of flights to a majority of gate areas except Concourse C. 

The St. Louis area utility, Ameren, has estimated power could be returned by Saturday night. 

National Weather Service meteorologist Scott Truett confirmed Saturday it was a tornado that struck the airport.

He said it was possible that a tornado that touched down near the St. Charles County town of New Melle was the one that ripped into the airport and apparently other parts of St. Louis County. If that was the case, the tornado sustained itself for roughly 30 miles.

"We think it touched down at New Melle and maybe lifted up and touched down again at the airport," Truett said. "We still have to connect the dots to be sure."

Missouri Gov. Jay Nixon announced late Friday he had declared a state of emergency, allowing state agencies to assist local jurisdictions with their emergency responses to the storm's aftermath, including the destruction at Lambert.

"The state of Missouri is ready to assist at every stage of this emergency to keep Missouri families safe and help communities recover," Nixon said.

For the last 12 hours, the airport has led an aggressive effort of cleanup in and around the complex. 

"We have all hands on deck here," St. Louis Mayor Francis Slay said at the airport. "This is something we're putting a lot of attention to."

In addition to Concourse C, Terminal 1 also suffered extensive damaged from blown windows and doors. An Air National Guard facility at the airport reportedly also was damaged.

"This landmark facility has taken a direct hit from a natural disaster," said U.S. Rep. Lacy Clay, D-Mo., at a Saturday morning news conference at Lambert. "We have reached out to the president to see what assistance we can get from FEMA."

But amid all the wreckage, there was relief that things could have been worse. Only five people with minor injuries were taken to the hospital from Lambert, while an unspecified number of others were treated at the scene for cuts blamed on flying glass.

"We want to thank our employees and all of our mutual aid support from surrounding communities for the immediate and sustained response to help our passengers, begin cleanup and work to get our operations started again," said Airport Director Rhonda Hamm-Niebruegge. 

The people who were transported to the hospital Friday have since been treated and released.Passengers from at least two planes were stranded briefly on the Lambert tarmac because of debris but were later taken away by buses. 

Dianna Merrill, 43, a mail carrier from St. Louis, was at Lambert waiting to fly to New York with a friend for vacation. She said her flight had been delayed by weather and she was looking out a window hoping her plane would pull up. But the window suddenly exploded.

"Glass was blowing everywhere. The ceiling was falling. The glass was hitting us in the face. Hail and rain were coming in. The wind was blowing debris all over the place," she said. "It was like being in a horror movie. Grown men were crying. It was horrible."

Merrill said she felt lucky to be alive and that airport workers quickly moved people to stairwells and bathrooms to get them out of harm's way.

St. Louis County Police Chief Tim Fitch, who was at the airport when the storm was closing in, said he saw gawkers watching the weather outside as the tornado sirens blared. Moments later, they hastily scrambled inside the building and sought shelter in a restroom.

"About the time we came into the building, the doors blew off," he said. "Literally 10 seconds later, it was over. It's amazing to me more people weren't hurt."

Elsewhere around St. Louis, residents in suburbs were waking to damaged homes, fallen trees and downed power lines -- the remains of a fierce line of storms that moved through central and eastern Missouri.

Unconfirmed tornadoes were reported in several counties in the St. Louis area, and at one point utility company Ameren Missouri reported more than 47,000 power outages, with another 7,000 reported in Illinois.

In the suburbs of Maryland Heights and New Melle, the storms damaged several dozen homes but there were no immediate reports of major injuries. Some playground equipment in New Melle was left in a twisted heap by the storm that also tore up roofs and ripped off siding.

Brandon Blecher, 16, said he was home watching the storm out his window in Maryland Heights when he spotted the tornado coming toward his house. A gust of wind knocked out his window.

"The giant wooden swing set in my neighbor's yard came into my yard and a shed landed on my deck," he said. "The tornado was right on top of us."

Maryland Heights police were dealing with reports of gas leaks and downed trees that were blocking roadways.

The city's community center was opened as a shelter Friday night for residents affected by the storm.

"We have electricity, and everything's fine," Vaughn said. "We have heat and air. We'll be here as long as we need to be."

Damage, possibly from a tornado, was also reported at several towns near the airport -- Bridgeton, St. Ann, Ferguson and Florissant. Interstate 270 in that area was closed. Trees and power lines were down. A tractor-trailer was sitting on its end.

In downtown St. Louis, Busch Stadium officials hurriedly moved Cardinals fans to a safe area as tornado sirens blared. The game with the Cincinnati Reds was delayed for hours but later resumed.

The Associated Press contributed to this report.