By Keith Coffman
DENVER (Reuters) - A Colorado wildfire raging out of control in the foothills and canyons near Denver has killed an elderly couple and destroyed 23 homes, and authorities warned on Tuesday that evacuation orders could be expanded to another 6,500 residences.
The blaze, thought to have been ignited by embers from a controlled-burn operation last week, has charred 4,500 acres.
About 900 dwellings were under mandatory evacuation orders, and residents of another 6,500 homes in the area were warned on Tuesday to prepare for possible evacuation because of a spot fire ignited by the main blaze, authorities said.
The spot fire could advance on those dwellings, which are spread across mountainous terrain. The main blaze, which has been called the Lower Fork Fire, is located in the foothills about 20 miles west of Denver, the state's most populous city.
The couple killed in the wildfire was identified as Linda Lucas, 76, and her husband Samuel Lucas, 77, said Jacki Kelley, spokeswoman for the Jefferson County Sheriff's Office. Another woman who lives in the fire zone remains missing, authorities said.
They said one of the bodies belonging to the couple was found inside a burned-out home while the other was discovered just outside. The bodies were located on Monday night and Tuesday.
Calmer winds on Tuesday allowed air tankers to make fire retardant drops after high winds grounded the fleet on Monday, said Steve Segin, spokesman for the Rocky Mountain Coordination Center. Also, two Colorado National Guard helicopters were making water drops on the blaze.
But Kelley said the blaze had still not been contained from any side, and put the number of homes destroyed at 23.
Lighter winds, higher humidity levels and cooler temperatures on Tuesday aided the 200 firefighters on the ground, before the weather turned against them and forced firefighters to retreat to protecting structures, officials with the Jefferson County Sheriff's Office said.
Crews from several other states were arriving to battle the blaze, and fire managers said they expect 450 firefighters to be on site by Tuesday night.
The Colorado Bureau of Investigation was investigating the origin of the blaze, but authorities said initial indications were that it was started by embers from a controlled-burn operation to remove vegetation in wildfire-prone areas.
(Editing by Alex Dobuzinskis, Cynthia Johnston and Eric Beech)