LOS ANGELES, Sept. 3 (Xinhua) -- Firefighters were battling two brush fires on Monday as unrelenting heat wave continued to sweep Southern California.

    Both fires were reported Sunday afternoon, one in the Lancasterarea and the other south of the Antelope Valley Freeway. Both fires, not far from Los Angeles, are threatening residential areas.

    About 350 firefighters continued to battle the blaze after crews in helicopters and air tankers shut down last night.

    Firefighters said the fire could burn for several days because of limited access to the area.

    "If this fire continues to spread, it could threaten ranch homes and private property within the forest, but it'll be a while before that happens," said Stanton Florea of the U.S. Forest Service.

    Hot, muggy conditions and dry brush hindered efforts to contain the blaze, he said.

    Meanwhile, the National Weather Service (NWS) is forecasting "excessive heat" and near-record high temperatures on Monday, with three-digit highs in many areas of Southern California.

    Valley areas could reach 100 to 110 degrees Fahrenheit (about 40 degrees Centigrade), and 97 to 106 in some mountain areas, where there's also a 20 percent chance of afternoon showers and thunderstorms.

    On Sunday, triple-digit temperatures were reached in many parts of the region, especially in the mountains and valleys, where the high was 112 degrees in Woodland Hills and Chatsworth, according to the National Weather Service.

    Monday is the seventh day of a heat wave that has contributed to blackouts leaving thousands without air conditioning.

    About 3,500 customers in scattered parts of Los Angeles still had no electricity early Monday, Los Angeles Department of Water and Power (DWP) spokeswoman Mary Anne Piersen said.

    "Probably more than 90 percent of them are due to stress on the system due to the heat," she said. "Different pieces of equipment get fatigued and blow out, so they have to be replaced."

    Lightning striking power system equipment during scattered desert thunderstorms added to the strain on the system.

    Some 20,000 customers of Southern California Edison power company in Los Angeles, Orange, Ventura, Riverside and San Bernardino counties also had no electricity, spokesman Steve Conroy said.

    "We expect at this point to make solid progress at getting a lot of the service back during the morning and midday hours," Conroy said.

    Dozens of cooling centers were opened across California on Sunday for people who had no air conditioning.