FLAGSTAFF, Ariz. -- Massive clouds of smoke choked Flagstaff on Tuesday as firefighters battled to keep a nearly 19-square-mile wildfire from heading toward the mountain town of about 60,000 people.

The work shifted after firefighters secured the area closest to homes, several hundred of which remained under evacuation orders, said fire spokeswoman Erin Phelps. Crews will work on containment lines on the south and north sides where the fire is most active, she said.

"It's comforting to know the east side is fairly secure so we can start focusing on those other areas," Phelps said.

The fire is about five miles from Flagstaff on the southernmost edge where rocky terrain and rolling hills make the terrain more difficult for fire crews to access.

The wildfire that has sent massive clouds of smoke over parts of the city was estimated at 12,000 acres late Tuesday afternoon, a result of operations to rob the fire of fuel and new growth on the south and north sides.

Four heavy air tankers were on standby. They're capable of carrying more than 2,000 gallons of fire retardant used to slow the spread of fire. The tankers are part of 19 under contract through the U.S. Forest Service to fight fires across the country.

Strong winds had quickly fanned the fire that broke out Sunday. Winds predicted at up to 18 mph with 22 mph gusts were expected to decrease later Tuesday afternoon.

Residents who showed up at a shelter at lunchtime were still waiting to hear how long they had to be out of their homes. Tracey Simpson, who has stayed in hotels the past two nights, learned she would have to find a room for yet another night.

Simpson and her husband moved to Flagstaff from Pennsylvania five weeks ago and were forced to evacuate on Sunday from the home they rent in the fire area.

She has no assurance of recovering any possessions if they were lost to the flames.

"We were unprepared," Simpson said. "I forgot to get renter's insurance."

Staying in hotels is getting expensive, she said, and they can't bring their two dogs along to sleep at a shelter.

"I have never experienced anything like this," Simpson said. "We just want to go home."

Percy Piestewa said her family has not been allowed to return to their home since Sunday, but she's not worried.

"You just have to leave everything up to God.

Piestewa said the family was staying with friends and attending briefings at the Red Cross shelter. She is the mother of Army Spc. Lori Piestewa, who was killed in Iraq in 2003.

About 10 percent of the so-called Schultz fire was under control as 800 firefighters worked to suppress it. No major injuries have been reported and no structures have burned.

Conditions are dry, despite record amounts of snowfall in the area last winter. Authorities say campfires are to blame for the Schultz fire and another smaller one in southeast Flagstaff. They will be prohibited in three Arizona forests starting Wednesday.

The fire in southeast Flagstaff was 80 percent contained Thursday afternoon. A third fire 11 miles northeast of Williams was expected to be fully contained Wednesday.

President Obama spoke with Arizona Gov. Jan Brewer on Tuesday to assure her of the federal government's continued support in firefighting efforts, according to a news release from the White House. Two requests from the state for federal fire management assistance funds have been granted, it said.

In Colorado, firefighters battled a 700-acre wildfire Tuesday west of Canon City near the scenic Royal Gorge Bridge. The blaze forced an unknown number of residents from their homes and destroyed several structures. It wasn't immediately known whether any of those were homes.

The suspension bridge that crosses the 1,200-foot deep gorge over the Arkansas River remained off limits. River rafting through the gorge has also been shut down because of the fire.