Rain extinguished most of the fires in Southwest Virginia and across the Southeast United States yesterday, giving exhausted firefighters and emergency crews a reprieve from a string of sleepless nights.

While the wet weather was a welcome relief, firefighters said the rainfall was not heavy enough in many parts of Southwest Virginia and elsewhere to soak the foot-high layer of dry ground cover, leaving many firefighters concerned that the danger is not yet over.

"We're just not calling off the dogs, per se," said Terry Lewis, a fire official with the U.S. Forest Service's regional headquarters in Atlanta.

Investigation into the causes of the worst rash of autumn fires in a generation were continuing and at least 11 persons have been arrested on arson-related charges in Tennessee and Alabama. A 16-year-old was arrested in Virginia last week in connection with a fire in the southwest part of the state.

Early yesterday, the 870 National Guardsmen working in Virginia, Kentucky and West Virginia retreated and hundreds of volunteer teen-aged firefighters were sent home as one-half to two inches of rain were reported to have doused or slowed still smoldering fires.

An estimated 350,000 acres were burned in more than 10,500 fires in the Southeast since Halloween, most of them set by arsonists. A low-lying cloud of smoke from the fires had covered much of Virginia, Washington and Maryland during the weekend.

"We won't be smelling up the whole Southeast anymore," said Townley Bergmann, chief of special projects for the Kentucky Division of Forestry, which reported that 1,431 fires had burned 113,924 acres in the state.

A low pressure area swept moisture in from the Gulf of Mexico on Monday, but dumped less than a quarter of an inch in Alabama, Kentucky, Tennessee, Georgia and West Virginia. Virginia fire officials monitoring the weather said the dry southwest, the fire hot spot, received only a half inch of rain. Nearly an inch of rain was reported in other parts of the state.

The National Weather Service predicts rain changing to light snow today in the Washington area, and in Virginia and parts of Kentucky and West Virginia where fires were located. Temperatures will fall to the low to mid-40s and there will be gusty northeast winds of 15 to 25 miles an hour, the Weather Service said. No accumulation of snow is expected.

A winter weather warning was posted yesterday for parts of Maryland, West Virginia and northwest Virginia, with freezing rain, sleet and light snow in the forecast.

"It's the first bona fide storm of the season," said forecaster Calvin Meadows.

Fire officials said the rain has given exhausted crews, many of whom worked more than a week on little sleep, a chance to recuperate.

"Five hours of sleep knowing it's raining is a lot better than 10 hours {of sleep} when you know it's not raining," said Harold Hannah, regional forester in Virginia's southwest headquarters in Abingdon.

Near Washington, three fires on the Quantico Marine Corps base, which started Sunday afternoon, burned 1,000 acres, a fire department source said. The fires started near David's Crossroads on the western end of the base, in an area used as a firing range. An unexploded shell may have been the cause, the source said. No injuries were reported.