By Keith Coffman
DENVER (Reuters) - A wind-driven wildfire destroyed an unknown number of homes and forced the mandatory evacuation of 900 dwellings in the foothills and canyons west of Denver on Monday, authorities said.
The blaze, which also forced the closure of some roads in the area, was believed to have been ignited by embers left over from a controlled-burning operation conducted last week to clear parched vegetation that authorities wanted to remove as potential wildfire fuel.
As of nightfall, the blaze had scorched some 3,000 acres of grasslands and trees as it burned out of control roughly 20 miles from the western edge of Denver, the state's largest and most populous city, Jefferson County Sheriff's Office spokesman Mark Techmeyer said.
"Tonight firefighters are in a defensive posture, trying to protect structures," he told Reuters.
He said an undetermined number of houses had been lost to the fire, but the precise damage toll was not expected to become clear until after sunrise.
No injuries have been reported.
Fire personnel from 30 engine companies and 15 different agencies were assembled to battle the blaze, Jefferson County authorities said.
Rolling plumes of thick smoke from the fire drifted over Denver's southern suburbs and were visible throughout the metropolitan area during the day.
Single-digit humidity values, winds blowing at 40 to 50 miles per hour and a lack of snowfall during the past month put most of eastern Colorado under a red-flag warning for high fire danger on Monday, the National Weather Service said.
The high winds also had prompted flight delays at Denver International Airport.
Steve Segin, spokesman for the Rocky Mountain Coordination Center, said air tankers have been on alert for the last week in anticipation of extreme wildfire hazards in Colorado, but the gusty winds have grounded the fleet.
"There is really not much that can be done from the air until the winds subside," he said.
(Editing by Dan Whitcomb, Steve Gorman and Tim Gaynor)