D.C. police are investigating whether last Friday's $250,000 fire at Weatherless Elementary School and three others in a three-block area of Southeast Washington may have been set by the same arsonist.

Arson Squad Det. Donald A. Smith said that at least three of the four fires, including the one at Weatherless that forced the closing of 10 classrooms, apparently were started with a flammable liquid. There also is evidence that a forced entry was made at all four locations.

"We're more or less investigating each one separately but keeping in mind the similarities and the possibility it could be the same person," Smith said.

No arrests have been made, but Smith said police believe a young man between 17 and 22 is probably involved.

"School fires are usually set by young males, possibly a dropout, someone who didn't like school," he said.

But otherwise, Smith said there does not appear to be any motive for the three other fires, "unless it's just a pyromaniac, someone who enjoys watching fire."

On Saturday morning, the day after the fire at the school, $5,500 in damage was caused by a fire in a vacant apartment at 3910 Burns Place SE. On Jan. 29, two fires caused $5,000 in damage in a recently renovated corner rowhouse at 3984 East Capitol St. and two fires in mid-January caused relatively minor damage in a vacant two-story rowhouse at 3933 C St. SE. The C Street and Burns Place buildings are part of the Stoddert Terrace public housing project.

No one has been injured in any of the fires.

One fire investigator described the spate of fires as "an unusual number of incidents" for one area, in such a short time.

The most serious of the fires -- the one at Weatherless -- severely damaged four classrooms and left six with smoke damage. Principal Shirley McGalliaria said yesterday she did not know whether the damaged portion of the school could be used again this school year.

While students were shifted to other classrooms yesterday, workmen with the city's Department of Environmental Services backed a garbage truck up to the damaged wing of the school and shoveled mounds of charred school workbooks, twisted furniture and other debris into the truck.

While much of the recent work of the Weatherless pupils was destroyed in the fire, one partially blackened poster dangled in the wind on an outside door yesterday. It reminded the school children to walk in a line during fire drills.

A-1 Realty, a part owner of the two-story rowhouse on East Capitol Street, said the renovation of the house had just been completed when the two fires were set, one charring part of the kitchen and the other damaging second floor rafters.

While the two fires were confined to relatively small areas, firefighters had to chop through a first-floor ceiling and upstairs walls to get to the rafter fire.