MEYERS, Calif. -- A growing army of firefighters launched an aggressive attack Monday to corral a forest fire that had destroyed more than 200 buildings in less than a day and forced about 1,000 people to flee neighborhoods near the southern edge of Lake Tahoe.

State officials declared a state of emergency in the area Monday, the first step in requesting emergency federal assistance to fight the blaze, which rained ash on the pristine lake and darkened the sky over the high Sierra.

"The circumstances of this wildfire, by reason of their magnitude, are beyond the control of the services, personnel, equipment and facilities of any single county," said Lt. Gov. John Garamendi, who signed the declaration while Gov. Arnold Schwarzenegger was in Europe.

The fire, believed to be caused by human activity, had charred nearly 2,500 acres -- nearly 4 square miles -- since it started Sunday afternoon. No injuries were reported. The state Office of Emergency Services said 165 houses and 75 outbuildings had been destroyed.

The blaze was less than 10 percent contained Monday, said Lt. Kevin House of the El Dorado County Sheriff's Department.

"This is far and above the biggest disaster that has happened in this community, I don't know, probably in forever," House told reporters in an early morning briefing.

Flames came within a quarter mile of the 1,500-student South Tahoe High School during the night, and dozens of firefighters surrounded the school. A layer of black ash floating on the lake lapped at boat docks along the shore.

Wind slowed to about 12 mph during the night, after gusting as high as 35 mph late Sunday, and temperatures dipped into the 30s, aiding firefighters' efforts to corral the flames in the heavily wooded, parched terrain.

However, the fire spread northward, enveloping hundreds of acres of unpopulated mountainside, and fire officials warned that afternoon wind could turn the flames toward the east and threaten hundreds more homes.

The number of firefighters battling the blaze was nearly doubled Monday to more than 700. However, air tankers and helicopters were grounded by dense smoke that cut visibility.

Fire officials said they have two days to get the fire under control because high wind and low humidity are forecast for Wednesday. "We have a window right now where we're really trying to aggressively attack this fire," said Daniel Berlant, a spokesman for the California Department of Forestry and Fire Protection in Sacramento, Calif.

The National Weather Service issued a dense smoke advisory warning people from South Lake Tahoe to Carson City, Nev., that the heavy airborne ash would make it difficult to see and breathe.

House said there were no reports of people missing in the fire area, but "the truth is we haven't really been able to get in there and see."