MEYERS, Calif. – A growing army of firefighters launched an aggressive attack Monday to corral a forest fire that had destroyed at least 220 homes in less than a day and forced about 1,000 people to flee neighborhoods near the southern edge of Lake Tahoe.

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.

It was less than 10 percent contained Monday morning, 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.

The National Weather Service issued a dense smoke advisory warning people from South Lake Tahoe to Carson City 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.”

Residents and campers sought shelter at evacuation centers in South Lake Tahoe and at the homes of friends and the area’s many hotels, some of which provided free rooms.

Matt Laster showed up at one evacuation center Monday looking for clothes. He said he and his wife, two young children and cat fled their rented home Sunday, and lost “all the memories,” including his Star Trek collectibles and Grateful Dead albums.

“We are doing OK. I think we are going to get resettled pretty quickly,” Laster said.

Steve Yingling, sports editor for the Tahoe Tribune newspaper, lives near where the fire started and had little hope that his home survived. He was leaving for work Sunday afternoon when he heard sirens.

“I looked back and saw the huge plume of smoke,” he said on Monday. “That’s when I really started to get scared because I know the danger alert that we’ve had in this area.”

State and federal fire officials had warned of a potentially active wildfire season in the Sierra Nevada following an unusually dry winter. The annual May 1 snow survey found the Tahoe-area snowpack at just 29 percent of normal levels, the lowest since 1988.

Earlier this month, a fire forced residents to flee the eastern Sierra community of Coleville.

Elsewhere, at least 30 people had left their homes near the Southern California town of Rosamond, some 80 miles north of Los Angeles, because of a 6,000-acre brush fire, officials said Monday. There had been no reports of damage to houses from the day-old fire, Kern County fire engineer Michael Nicholas said.

Crews in Alaska worked to protect hundreds of homes in the hills of the scenic Kenai Peninsula. It had burgeoned to 81 square miles since Tuesday, consuming 35 far-flung cabins in the Caribou Hills, state fire information officials said. Forty other structures, including sheds and outhouses, were also lost in the popular hunting and snowmobiling area about 80 miles south of Anchorage.

The fire threatens 600 more homes and cabins, Hall said. An evacuation order has been in effect since Friday, but fire officials said an unknown number of residents have refused to budge.