The Waldo Canyon Fire, which tore into the outskirts of the state's second largest city Colorado Springs earlier this week, has destroyed at least 346 houses and forced some 36,000 people to evacuate, according to officials.

Ahead of his visit, Obama declared a "major disaster" in Colorado, releasing federal funds to aid local efforts to help evacuees.

Late Thursday, Colorado Springs Police Chief Peter Carey announced the first casualty of the blaze, saying a body had been found in the burned-out rubble of a house and that another person was missing who lived at the same address.

The fire has torched some 16,750 acres (6,700 hectares), officials said, revising downward an earlier estimate.

The blaze is just 15 percent contained, and is one of several wildfires straining firefighting assets across the front range of the Rocky Mountains, a major destination for winter skiing and adventure sports.

Officials in Colorado Springs had planned to meet privately Thursday night with homeowners -- many of whom fled with no time to collect their belongings -- and asked reporters to respect residents' privacy following the meeting.

"It's going to be a tough evening, but we're going to get through it," a weary-looking Colorado Springs Mayor Steve Bach said earlier, adding that the Red Cross, chaplains and other counselors would be present.

"The one positive note was that many businesses and individuals had offered help to victims," he said.

Colorado Springs's daily newspaper, The Gazette, reported that a few people had been arrested for trying to sneak into areas that had been evacuated, and Carey said there had been a "small number of property crimes."

Lower temperatures and higher humidity meanwhile finally gave firefighters a much-needed break on Thursday, and officials were allowing some evacuees to return to their homes.

"We made significant progress today. The weather has cooperated as it has on no other day," Jerri Marr, supervisor of the Pike and San Isabel National Forests, told reporters.

Tom Harbour, the director of fire management at the US Forest Service, said federal authorities would make every effort to provide resources to battle "some of the most challenging wildfires we've experienced in years."

More than 8,800 firefighters were battling some 41 major wildfires across the United States on Thursday, using 21 air tankers, more than 550 fire engines and 170 helicopters.

About half of the federal resources were stationed in Colorado, where 11 wildfires have scorched nearly 160,000 acres.

The Waldo Canyon blaze forced the evacuation of the nearby US Air Force Academy, where cadets joined fire crews in protecting their barracks and other buildings as the fire swallowed 10 acres of the academy's land.

"This is absolutely the worst wildfire I've ever seen," said Ernst Piercy, the Academy's fire chief.

Summer wildfires are common in the mountains of arid Colorado but rarely burst into residential areas, as the Waldo Canyon Fire did earlier this week. It is not yet known what sparked the blaze, which erupted on Saturday.

Record high temperatures, extremely low humidity and wind gusts of up to 60 miles (100 kilometers) an hour have fueled fires across the American West, where an unusually mild and dry winter left widespread tinder-like conditions.

The High Park fire -- sparked by lightning in a more remote area northwest of Denver -- is the second biggest in the state's history.

It destroyed 257 homes and ate through 87,284 acres but is now 75 percent contained, Larimer County officials said.