A dangerous wildfire that threatened the popular California tourist destination of Idyllwild remained just 15 per cent contained Friday as volatile weather threatened to undo gains made since Thursday by firefighters. According to the National Interagency Fire Command, the Mountain fire had burned more than 10,000 hectares and destroyed seven houses. More than 3,300 firefighters were battling the blaze, aided by 20 helicopters, which flew through the night Thursday in an attempt to halt the advance of the flames. Some 6,000 residents of the mountain town of Idyllwild and the surrounding communities some 180 kilometres east of Los Angeles were evacuated. The fire broke out Monday and now threatens about 4,000 homes, dpa quoted authorities as saying. "Fire conditions today are conducive to extreme fire behaviour given unstable atmospheric conditions," incident commanders said Friday morning. "A large smoke column could form over the fire and then produce thunderstorms. Strong down drafts winds could develop, potentially causing spot fires and rapid fire growth."