© AP Photo/Mark Leffingwell
A home destroyed by a wildfire is shown in an aerial photo over Boulder, Colo., Wednesday, Sept. 8, 2010.
Hundreds of residents evacuated by a wildfire that has destroyed at least 169 houses in the Colorado foothills were being temporarily allowed back to their homes Thursday.

Firefighters were also working to make progress containing the fire ahead of strong winds expected later in the day. Gusts of up to 60 mph could blow away the little moisture the area has seen and spread the fire beyond the 20-mile-long perimeter.

Containment lines have been built around 30 percent of the fire, but firefighters warned that progress could be undone.

"The wind event tonight, we could be off to the races," said Rob Bozeman, field observer with the Boulder Mountain Fire Protection District.

Authorities are allowing residents to enter the burn area in two waves Thursday to do things like pick up pets and supplies, but sheriff's Cmdr. Rick Brough said the expected change in the weather make it too dangerous for people to remain in their homes. He urged residents to take care of business as quickly as possible and then leave again, noting that people would be on the honor system.

Nine people had been reported missing in the fire zone but Brough said they all have been accounted for.

About 3,500 people have been out of their homes for four days, and some residents have been frustrated with a lack of information about what was happening behind fire lines or because they couldn't do more to help. Some have gotten around roadblocks by hiking and biking in to check on their homes.

Brough said one person caught sneaking in was led away in handcuffs. He acknowledged authorities didn't have enough resources to force everyone to leave again if they refused to do so.

The fire has burned 6,365 acres, or about 10 square miles, and damage in about 20 percent of that area still has not been assessed.

Already though, the reported loss of homes surpasses that of the 2002 Hayman fire in southern Colorado that was the most destructive in the state's history. That fire destroyed 133 homes and 466 outbuildings on 138,000 acres of more sparsely populated area that includes national forest land.

Firefighters took advantage of cooler weather and light rain to attack the wildfire Wednesday, and air tankers dumped fire retardant on the flames. A total of 100,000 gallons of retardant has been used and firefighting costs have reached $2.1 million so far.

The cause of the fire was under investigation.

Fire managers said as many as 500 firefighters and support personnel are at the fire and more were on the way. Laura McConnell, spokeswoman for the management team, said crews are dealing with downed power lines, debris, poison ivy and rattlesnakes. They also have to watch for propane tanks in the area.