Unidentified assailants slashed the throats of four persons in a Fairfax County apartment yesterday in an attack that left all four victims injured, two critically, police said.

In first reports police said they could give no motive for the attack, which occurred about 2:30 p.m. in an apartment at 9136 Barrick Rd., north of Rte. 50 and east of Fairfax Circle.

However, preliminary investigation indicated that a stereo set was missing from the third-floor apartment where one of the victims apparently lived and the other three apparently are visiting, police said.

Relatives and acquaintances' identified the victims as Stephen Dowell, 19, of the Barrick Road address, Laura Bombere, 18, David C. Perash, 21, who recently moved from the Washington area to Hanover, Pa., and Debra Telford, 20, of 2530 Leeds Rd., Oakton.

All four were reported to be in surgery last night at Fairfax Hospital. Authorities there said both Perash and Dowell were in critical condition. The other two victims were listed in fair condition.

County police Sgt. Ernie Jenkins said few details of where happened in the apartment were available immediately because detectives have been unable to interview the victims.

A police spokeswoman said authorities learned of the incident after one of the victims went downstairs to ask a neighbor to call police.

Craig Beamer, a resident of the building, part of the Providence Hall development, said he heard banging on his door about 2:30 p.m. and opened it to find a woman outside, with a blood-stained towel wrapped around her neck. She was screaming, Beamer said, and she asked him to call the police and an ambulance.

Few other residents of the brick, 14-unit building where Beamer said he pays $291-a-month rent for a two-bedroom apartment, were reported home at the time.

Larry Buettner, a resident who saw the victims being brought out, bandages around their necks, said he knew little about them.

"People in this building don't mix well," said Buettner, who said the neighborhood included a good proportion of transients.

Police said they received preliminary reports indicating that the attack may have been carried out by four men, one wearing a green hat. Few other details were available.

According to family members and others, Perash had moved to the Hanover, Pa., area to be receiving manager at The Low's hardware and lumber company warehouse there.

They said he frequently came here on weekends to visit Telford, a student at George Mason University who has a job as a ticket taker and usher at a Fairfax Circle movie theater.

Perash and Telford were described as friends of the other two victims, Dowell and Bombere. Dowell reportedly worked for the Vienna branch of the same hardware company that employs Perash.

A relative said Bombere worked for Biotechnology, a research and development laboratory in Falls Church.

Police who emerged from the apartment where the attack occured said blood stained a wide area. According to one report, some of the victims may have been bound before being attacked. There was no indication of forced entry, according to investigators.