SWORDS CREEK, VA., NOV. 7 -- A low-hanging cloud of smoke dimmed skies over much of Virginia today as scores of arson-caused fires, spurred by shifting winds and dry ground cover, burned out of control in the state's forest and coal country.

Despite the overnight efforts of hundreds of exhausted firefighters, many of them volunteers, fires in the southwest part of the state played a fanciful game of hide-and-seek -- dying out during the early morning, then rekindling within hours.

Smoke streaming north and east from the fires filled Washington area streets with a haze tonight, diffused light from streetlamps and reduced visibility at National Airport to about three miles from the 15 miles that was reported earlier today.

National Weather Service forecaster Scott Prosise reported that a woman in Garrett County, in far Western Maryland, said smoke was so thick that "she can't go outside without coughing."

Air pollution and Weather Service officials said that the smoke posed no significant health hazard in the Washington area. But they suggested that children, the elderly and people with respiratory ailments should limit outdoor activities in parts of Virginia where the smoke was thickest.

Major blazes were reported in Lee, Smyth, Russell, Buchanan, Craig and Tazewell counties in southwest Virginia, most of them out of control. Fire officials here estimated that 78 fires, at least half of them deliberately set, have occurred in the past week. They have consumed about 4,000 acres.

Also, a fire 15 miles north of Roanoke in the Barbours Creek wilderness study area has consumed 1,850 acres, most of it public land, U.S. Forest Service officials said.

Weather satellite pictures showed smoke from fires in southwest Virginia, eastern Kentucky and West Virginia reaching more than 100 miles off the East Coast, ranging from the Delaware border to Norfolk, according to the National Weather Service.

No injuries were attributed to the fires. However, thick smoke was called a factor in a collision between a church choir bus and a stalled pickup truck today on the West Virginia Turnpike that killed a Virginia boy and injured 23 people, state police said.

Rain is not expected to help in fighting the fires until late Sunday and during the day Monday, according to the weather service.

Nature and the mischief of man have kept old fires in southwest Virginia alive and started new ones. Dry conditions have created a dense ground cover of fallen leaves and branches, a bed in which fires sleep but do not die.

What the people in this area call "an evil tradition" of arson has been responsible for at least half of the fires here, including a 300-acre blaze that began early this morning.

By midday, the steep ridges of coal-producing mountains known here as Miller Creek were blackened.

Puffs of smoke from burning trees and smoldering white ashes rose to form an eerie haze that made it impossible to see into the hollows the people of this region call home.

"It's been so smoky in there, you can't see," said Swain Perkins, a gravel hauler who took his four-wheel-drive vehicle into the middle of the smoldering ashes to check on his satellite dish and two horses.

Surveying the area, he found the destruction unthinkable. "I don't think they do it to kill the game. I just think they do it for something to do," he said. "It will just be someone whose wheels are grinding."

This area 15 miles north of Honaker has witnessed manmade fires every dry season for 20 years, said Harold Hannah, a forester in the Abingdon regional office of the Virginia Department of Forestry.

Local residents say they, too, are baffled by the recurring blazes. Many of the locals say these have been set each year for as long as they remember.

"It's like somebody's stepping on the gas," said Michael Whited, sitting with his brother and two sons at the edge of the burn, a ridge leveled by strip mining. "People, they just do it to do something. Just to destroy."

This pastime has led to firefighter Allen Doss' marathon. He was sent here from Abingdon at 2:30 this morning with three hours of sleep after working a fire in Washington County.

His face covered with soot and his eyes bloodshot, he spent a six-hour stretch on his bulldozer, trying to clear a path that would stop the spread of the flames.

"A bed would sure look nice right now," he said, leaning back in the seat of his bulldozer. "You think you've got it. You go home and take a shower and lie down, and two or three hours later they call you back."

Because the ground cover is so thick, it is useless to try to extinguish the fires, firefighters say.

No evacuations have been reported in any part of the state.

Staff writer Martin Weil contributed to this report.