(AP) - A wildfire that destroyed at least six homes, damaged 15 others and threatened hundreds more grew quickly Sunday as it triggered evacuations for nearly 3,000 people and burned dangerously close to communities in the parched mountains north of Los Angeles. The blaze had burned about 35 square miles of very dry brush in the Angeles National Forest mountains and canyons, some of which hadn't burned since 1929. The fire was growing so fast, and the smoke was so thick, that it was difficult to map the size, U.S. Forest Service Incident Commander Norm Walker said. "This is extremely old, dry fuel," Walker said at an afternoon news conference. The fire, which was 20 percent contained, appeared to be the fiercest of several burning in the West, including two in New Mexico, where thick smoke covered several communities and set a blanket of haze over Santa Fe on Saturday. Crews fighting the two uncontained wildfires focused Sunday on building protection lines around them amid anticipation that a forecast of storms could bring moisture to help reduce the intensity of the fires. The fire raging in Southern California had crews fighting the fire on four fronts, with the flames spreading quickest into unoccupied land, authorities said. But populated areas about 50 miles north of downtown LA remained in danger, with more than 2,800 people and 700 homes under evacuation orders in the communities of Lake Hughes and Lake Elizabeth, sheriff's Lt. David Coleman said. They wouldn't be allowed to return home until at least Monday and possibly Tuesday, Coleman said. About 2,100 firefighters aided by water-dropping aircraft, some of which were making the rare move of flying through the night, were attacking the blaze. "We're putting everything that we have into this," Walker said. Three firefighters had minor injuries, but no one else was hurt. Winds were blowing 20-25 miles per hour with gusts of more than 40 mph, so fast that speakers at the news conference were difficult to hear with hard winds hitting the microphone. "That has created havoc," LA County Deputy Chief David Richardson said through the winds. It's had a huge impact on our operations. At least six homes burned to the ground overnight, and 15 more were scorched by flames, LA County fire Chief Daryl L. Osby said. Temperatures hovered in the high 90s, but were expected to dip, with humidity rising, later Sunday. Patty Robitaille, 61, grabbed personal photos and documents before fleeing her Lake Hughes home with her pit bull, Roxie, as flames approached late Saturday. She said her property was in the direct path of the fire. A huge plume of smoke could be seen from much of various parts of northern Los Angeles County, and air-quality officials warned against strenuous outdoor activity. Several power lines were downed by the flames. The wilderness area is a draw for boaters, campers and hikers. Crews and residents were being warned to keep an eye out for rattlesnakes and bears that could be displaced by flames. In New Mexico, the forecast for moisture was not entirely good news. The potential thunderstorms also brought the possibility of lightning that could start new fires and gusty winds that could fan the blazes. The fire burning in New Mexico's Santa Fe National Forest 25 miles from Santa Fe had grown to nearly 12 square miles Sunday. Weber reported from Los Angeles. Associated Press writer Andrew Dalton also contributed to this story.