By Keith Coffman

DENVER (Reuters) - Two men from Alabama have been arrested in Colorado on arson charges accusing them of leaving a campfire unattended, igniting a blaze that destroyed five homes and forced the evacuation of nearly 2,000 residents, authorities said on Monday.

Andrew Suggs, 28, and Zackary Ryan Kuykendall, 26, set the "ad hoc" campfire over the weekend on private property outside the town of Nederland, Colorado, about 35 miles northwest of Denver, the Boulder County Sheriff’s Office said in a statement.

“The men did not ensure that the fire was properly extinguished by dousing it with water, or making sure the ashes were cool to the touch before leaving the site,” the statement said, adding that winds blew embers through the mountain canyon, sparking the blaze.

The so-called Cold Springs fire has blackened 600 acres, torched five houses and several outbuildings was continuing to burn unchecked as of Monday morning, Boulder County spokeswoman Gabi Boerkircher said.

The two men, both from the northern Alabama community of Vinemont, were charged with felony arson because “lives were endangered as a result of the fire,” police said, though no injuries have been reported.

Both men were due to make their initial court appearance on Monday.

The blaze near Denver was one of several firefighters have struggled to contain across Colorado amid hot, dry, windy weather gripping much of the state.

A 5,100-acre wildfire raging through two national forests in south-central Colorado has forced the evacuation of two campgrounds, while residents of nearby communities were placed on standby to leave their homes if winds blow flames in their direction, the U.S. Forest Service said on its website.

A separate fire burning since last month through remote forests farther north has grown to nearly 19,000 acres, creeping across the state line into Wyoming, said Lynn Barclay, a spokeswoman for the fire management team of that blaze.

That blaze, just 5 percent contained, was roaring through large stands of beetle-killed trees, and may continue to burn until late October, she said.

Farther west, the U.S. Bureau of Land Management said two of its firefighters were killed and a third injured on Sunday in a single-vehicle accident outside Winnemucca, Nevada, while they were scouting for possible fires from lightning strikes.

(Editing by Steve Gorman and Jeffrey Hodgson)