D.C. police divers equipped with metal detectors searched the McMillan Reservoir in Northwest Washington yesterday in an effort to find guns believed used by the robbers who shot and killed an off-duty Prince George's County police officer Feb. 8.

Police said they had reason to believe the guns were thrown into the reservoir, which is near Howard University Hospital. One of the suspects in the slaying, suffering from a gunshot wound, was left off at the hospital following the Feb. 8 shooting incident. Results of yesterday's underwater search were not disclosed.

A similar search of the Potomac River off Hains Point was made Thursday with the aim of recovering the service revolver of the slain officer, Raymond Hubbard, who had tried to intervene when he came upon a holdup in progress at the Iverson Mall shopping center in Prince George's.

Four suspects have been arrested and a fifth was still being sought yesterday.

Two of those in custody were inmates at a D.C. halfway house at the time of the shooting. One of those, Ronald Wayne Drake, 24, was a resident of the Community Correctional Center No. 1 at 1010 N. Capitol St., where he had been placed in a work release program from Lorton prison to serve sentences for attempted petty larceny and heroin possession. He was scheduled to be paroled from the halfway house Feb. 11, a corrections department spokesman said.

Terrance Antoine Harris, 21, had been convicted of robbery in 1980 and also was enrolled in a work release program at the halfway house. Police suspected his involvement in the Iverson Mall shooting when he failed to return to the halfway house facility after work and was reported admitted to Howard University Hospital with a gunshot wound.

At a press conference Wednesday, County Executive Lawrence J. Hogan said efforts to rehabilitate criminals through halfway houses had "failed miserably. Some of these people are just bad people, and they're not going to change."

Police gave corrected addresses yesterday for the other suspects in custody. They said Harlow Sails lives at 6149 64th Ave., Riverdale, and his brother Horatio Sails lives at 5715 83rd Pl., New Carrollton.