LOS ANGELES, Aug. 31 (Xinhua) -- Two firefighters were killed and five civilians were trapped on Monday as a massive wildfire continued its multi-direction spreading through the Angeles National Forest, authorities said.

    The car the two firefighters were in ran off a mountain road on Sunday after being "overrun by a fast-moving fire," according to a county fire statement.

    Fire officials received word midday Monday that five people had been trapped on a ranch in a remote valley after having refused to heed evacuation orders issued two days ago.

    The fire was about 5-percent contained and full containment was not expected until Sept. 15, according to the U.S. Forest Service which said earlier full containment was expected on Sept. 8.

    Agitated by the news of the entrapped people, local authorities and fire officials again urged residents to evacuate.

    "What this says is listen, listen, listen," Los Angeles Sheriff's Department spokesman Steve Whitmore said. "Those people were told to get out two days ago, and now we are putting our people in danger to get them out."

    Rescuers were unable to reach the ranch area because of intense flames, he said, adding that they were waiting for the flames to pass over before attempting to approach again. Whitmore stressed, however, that the rescuers "are jeopardizing their lives as a result of this."

    The spokesman said 4,000 homes had been evacuated as of Monday morning, and at midday, the city of Los Angeles issued mandatory evacuation orders for the homes in the Sunland-Tujunga area.

    Esmeralda Bracamonte, a U.S. Forest Service spokeswoman, said that about 10,000 people had been evacuated, but the number of evacuees would grow as the day wore on.

    Fueled by bone-dry brush and soaring temperatures, the wildfire, known as Station Fire, was also burning close to Mount Wilson, which hosts a historic observatory and an array of telecommunication towers used by TV and radio stations and public safety agencies.

    Nearly all of the 22 Los Angeles TV stations transmit signals via those towers, and so do more than two-thirds of the region's FM radio stations.

    Loss of communications facilities there would cripple fire and police departments across Southern California, that not only use mountaintop transmitters to communicate but also relay signals from other mountaintop towers back to command centers via microwaves.

    "These are extremely crucial to the infrastructure and public safety protection, and the daily lives in the L.A. basin," said Mike Dietrich of the U.S. Forest Service.

    The wildfire, which broke out near a ranger station Wednesday afternoon last week, has spread to scorch 105,000 acres (42,493 hectares) of land by Monday afternoon, according to local broadcast reports.

    The fire has so far destroyed 21 homes and was threatening 12,000 more homes and 500 commercial buildings, the Forest Service reported.

    At least 2,575 firefighters and 54 hand crews (of wildland firefighters) were on the scene, along with 290 fire engines, six helicopters, seven helitankers, eight air tankers and 52 bulldozers.

    A 20,000-foot-high mushroom-shaped cloud of smoke and water vapor towering over northern Los Angeles could be seen from miles way and was making air quality unhealthful and in some places hazardous.