A plume of smoke rises behind homes on the Waldo Canyon wildfire west of Colorado Springs, Colo., on Wednesday, June 27, 2012. A large number of homes were destroyed by the fire Tuesday night in subdivisions west of Colorado Springs. Authorities say it remains too dangerous for them to fully assess the damage from a destructive wildfire threatening Colorado's second-largest city. (AP Photo/Ed Andrieski)

COLORADO SPRINGS, Colo. - A raging Colorado wildfire destroyed an estimated 346 homes this week, making it the most destructive fire in the western state's history, officials said.

Colorado Springs Mayor Steve Bach said city officials assessed the damage and that the number was subject to change.

From above, the destruction wrought by the fire becomes painfully clear: Rows and rows of houses — hundreds in all — were reduced to ashes even as some homes just feet away survived.

Amid the devastation in the foothills west and north of the state's second-largest city, there were hopeful signs. More than 120 soldiers helped stop flames advancing on the U.S. Air Force Academy and cooler conditions could help slow the spread of a fire that could become one of the most destructive in state history.

Authorities initially did not know the extent of the damage, saying it was difficult to assess because the fires and smoke were too intense. More than 30,000 people frantically packed up belongings Tuesday night as the flames swept through their neighbourhoods.

Community officials were planning to begin the process of notifying residents Thursday that their homes were destroyed. They planned to schedule meetings for residents of different streets to advise them personally that their homes have been destroyed.

Officials had not released such lists as of Thursday afternoon.

But for many residents, the official notification is a formality. Residents recognize their street on aerial pictures taken of the devastation and carefully scrutinize the images to determine the damage.

Aerial photos and video from The Associated Press and the Denver Post helped show the scope of one of the worst fires to hit the American West in decades.

On one street, all but three houses had burned to their foundations, said Ryan Schneider, whose home is still standing in a neighbourhood where 51 others were destroyed.

"I was real happy at first. My wife was happy," he said. "The emotion of seeing the other homes, though, was instant sadness."

Colorado Springs, about 60 miles (100 kilometres) south of Denver, is also home to the U.S. Olympic Training Center, NORAD and the Air Force Space command, which operates military satellites. They were not threatened.

Conditions were still too dicey to allow authorities to begin trying to figure out what sparked the blaze that has raged for much of the week and already burned more than 29 square miles (75 sq. kilometres).

President Barack Obama was to tour fire-stricken areas on Friday as hundreds of locals and some tourists who were staying at Red Cross shelters hoped life would return to normal soon. Many more stayed with friends and family.

The evacuated area is a mix of apartment complexes, single-family homes, hotels and developments such as technology parks, said Joe Raso, president of the Colorado Springs Chamber of Commerce.

As of mid-day Thursday, the fire was only 10 per cent contained. The cost of fighting the blaze had already reached $3.2 million.

The fire blackened up to 50 acres (20 hectares) along the southwest boundary of the Air Force Academy campus, said Anne Rys-Sikora, a spokeswoman for the firefighters. No injuries or damage to structures — including the iconic Cadet Chapel — were reported.

Fort Carson, an Army infantry post about 15 miles (24 kilometres) from the academy, sent 120 soldiers along with bulldozers and other heavy equipment to help clear a line to stop the fire on the academy. Rys-Sikora said the academy was not getting a disproportionate share of equipment and firefighters.

The Flying W Ranch, a popular tourist attraction near Colorado Springs, was severely damaged in the blaze. But authorities let people into the area to check on cattle. John Hendrix, who volunteers at the Flying W, said 47 animals were accounted for.

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Associated Press writers Dan Elliott and Rema Rahman in Denver, Chris Carlson in Colorado Springs, Mead Gruver in Cheyenne, Wyoming, Matthew Brown in Roundup, Montana, and Matt Volz in Helena, Montana, contributed to this report.

News from © The Associated Press, 2012