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 closing of some roads in the area, was believed to have been ignited by embers left over from a controlled-burning operation 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, Colorado’s most populous city, Jefferson County Sheriff’s Office spokesman Mark Techmeyer said.