- A fast-moving wildfire west of Fort Carson grows to 20,000 acres, officials say
- At least 18 buildings have been destroyed, hundreds more are threatened
- Larimer County officials say they are competing for firefighting resources
(CNN) -- Hundreds of families took refuge early Monday at a northern Colorado shelter, waiting for word whether a fast-moving wildfire that forced thousands to flee had destroyed their homes.
At least 250 firefighters, along with air tankers and helicopters, worked overnight to try to slow down a wildfire that has destroyed more than 20,000 acres, though authorities conceded there was little hope in stopping the fire that is being fanned by strong winds and dry brush.
Crews have had some success safeguarding some homes and businesses, though Larimer County Sheriff Justin Smith said "hundreds of homes" need protecting, ceding some may not be able to be saved.
At least 18 structures, a mix of homes and outbuildings, have been destroyed or damaged since the fire began Saturday morning, according to county emergency management officials and InciWeb, the U.S. multi-agency Incident Fire Response website.
"We know this number will increase once crews get their surveys done," according to a statement posted on the Larimer County Emergency Information website.
The wildfire's erratic nature, fueled by strong winds and dry brush, is complicating efforts: It is not just moving in one direction and, in some cases, is returning to scorch areas it had already burned, according to the sheriff.
"We have planned and trained for fires in every neighborhood. But this fire hit every neighborhood at once," Smith told reporters.
More than 2,600 evacuation calls went out by late Sunday, and crews have been working around the clock to warn residents in the path of the fire.
"Flames were licking at the units that were doing the evacuations," Smith said.
Heavy smoke from the fire forced authorities to order the evacuation of a middle school-turned-shelter in Laporte, officials said. Residents were relocated to the Larimer County Fairgrounds in Loveland.
Firefighters' primary goal is to get people out of harm's way and try to save as many buildings as possible, said Smith. Still, he admitted much is still beyond authorities' control, thanks to low humidity, high temperatures and dry brush fueling the flames.
The sheriff said there is one person unaccounted for "in a location we believe somebody could have been burned." He also said authorities are looking into a report that two hikers were missing in the area of the blaze.
A shortage of equipment and manpower was compounding the problem, though authorities said they hoped to remedy that. Regional resources are already deployed fighting other outbreaks, such as the massive Whitewater Baldy fire in New Mexico.
"We continue to compete for resources with other fires," according to a statement posted on the Larimer County Emergency Information web page.
Poudre Fire Authority Chief Tom Demint told reporters Sunday night that the fire is out of control and developing a plan without resources is difficult at best. Dozens of fire engines deployed can only do so much in corralling the charging blaze, he said.
"You do the math and you see what kind of (trouble) we're in," Demint said.
The Colorado Army National Guard was ordered into the fire fight Sunday following an executive order by Gov. John Hickenlooper, said Capt. Darin Overstreet, a spokesman for the Guard.
The National Guard's Blackhawk helicopters, equipped with water buckets, joined an increasing number of firefighting helicopters and air tankers being brought into the state to battle the fire. Air tankers from Canada arrived Sunday as well, officials said.
Firefighters hope to finally make progress against the fire by late Monday with cooler temperatures and calming winds predicted, county officials said.
While temperatures have cooled somewhat, officials say continued low humidity and winds will continue to fan the wildfire on Monday.
First measured at two acres early Saturday morning, the High Park fire has grown exponentially in the time since, including more than doubling in size over the course of Sunday.
Fire investigators believe the fire was started by a lightning strike, though an investigation is continuing, county officials said.
CNN's Greg Morrison and Chelsea J. Carter contributed to this report.
