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The Federal Bureau Investigation announced Wednesday that it would investigate the cause of a raging wildfire that displaced thousands of residents and an untold number of homes in Colorado.

"The FBI Denver Division is working closely with local, state, and federal law enforcement to determine if any of the wildland fires resulted from criminal activity," local FBI spokesman Dave Joly wrote in an e-mail statement to The Denver Post. "FBI personnel are supporting command post operations in the fire regions and offering assistance with managing the volumes of information related to these tragic events."

The Post’s report mentions a recent fires apparently set by a serial arsonist in a neighboring county, but points out that authorities have not given any theories on how the Waldo Canyon fire started.

The FBI will reportedly work with the El Paso County police to determine the start of the blaze.

Meanwhile, Tens of thousands of Colorado Springs residents forced from their homes by a raging wildfire took refuge with friends or family and crammed into hotels and shelters as Army troops helped firefighters protect the U.S. Air Force Academy from encroaching flames.

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The blaze was burning out of control early Thursday in the mountains and within Colorado's second-largest city, after more than 30,000 evacuees frantically packed up belongings and fled.

The wildfire was one of many burning across the parched West, blazes that have destroyed structures and prompted evacuations in Montana and Utah and forced the closure of a portion of Zion National Park.

Shifting winds Wednesday challenged firefighters trying to contain the 29-square-mile Waldo Canyon blaze and extinguish hot spots inside Colorado Spring's western suburbs. The National Weather Service reported 60 mph winds and lightning above the fire Wednesday afternoon, but winds were calmer by nightfall.

"It won't stay in the same place," said incident commander Rich Harvey.

Neighborhoods where explosions of bright orange flame Tuesday signaled yet another house had been claimed were still dangerous, keeping authorities away from being to assess the damage.

But an AP aerial photo taken Wednesday of one neighborhood showed dozens of heavily damaged or destroyed homes.

Ed and Florine Gigandet took refuge in a hotel in Manitou Springs, which days earlier had been evacuated when the same fire passed through. They fled their home as ash fell on their driveway from an ominous orange smoke overhead.

Trying to learn about damage, the Gigandets drove to near their west Colorado Springs neighborhood to talk to police officers and see the area. They scoured media photos and spent hours on the phone with friends for any scrap of information. Authorities told the Gigandets it could be at least week before they're allowed home.

"We only packed clothes for four days," Florine Gigandet, 83, a retired photo printer, said. "I really thought that we'd be gone for only a day."

The displaced residents took stock of what they left behind. Some sat in coffee shops, others stood on bluffs to keep an eye on their neighborhoods, and others met with insurance company representatives.

The fire moved so fast that Laura Oldland grabbed damp laundry out of her drier and threw it into a suitcase. But she forgot her grandmother's dishes.

The Gigandets, avid golfers, left their clubs behind. "We should be out golfing," said Ed Gigandet, 81, a retired mining machinery sales analyst.

Meanwhile, the White House said President Barack Obama will tour fire-stricken areas of Colorado on Friday and thank firefighters battling some of the worst fires to hit the American West in decades.

Colorado Springs Police Chief Peter Carey said Obama's visit to Colorado, considered a key battleground state in the presidential election, would not tax the city's already-strained police force. Gov. John Hickenlooper said he expected the president might sign a disaster declaration that would allow for more federal aid.

The fire burned about 10 acres along the southwest boundary of the Air Force Academy campus. No injuries or damage to structures — including the iconic Cadet Chapel — were reported.

Late Wednesday night, Air Force Academy officials announced they were relocating about 550 cadets off academy grounds. About 200 cadets in summer academics were being moved to the University of Colorado-Colorado Springs, and 350 others in airmanship and other training programs were released to local sponsor families, the school said. The cadet area isn't immediately threatened, and an incoming class of more than 1,000 is still scheduled to arrive Thursday.

About 120 soldiers from nearby Fort Carson built firebreaks around parts of the academy, aided by equipment including 10 heavy bulldozers, four excavators, 13 military transportation and support vehicles, and one commercial road grader, Army officials said.

The full scope of the fire remained unknown. So intense were the flames and so thick the smoke that rescue workers weren't able to tell residents which structures were destroyed and which ones were still standing. Steve Cox, a spokesman for Mayor Steve Bach, reported that at least dozens of homes had been consumed.

Indeed, authorities were too busy Wednesday struggling to save homes in near-zero visibility to count how many had been destroyed in what is the latest test for a drought-parched and tinder-dry state. At one point, a team assessing the damage had to leave charred neighborhoods because of smoke and fire danger.

Carey said officials had no plans to release the numbers of homes destroyed — insisting residents have a right to be told first, in private.

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The Associated Press contributed to this report