A 38-year-old undercover D.C. police officer was shot and seriously wounded last night during an exchange of gunfire in a dimly lit Northwest Washington schoolyard while trying to arrest several persons suspected of selling drugs, according to a police spokesman.

The officer, identified as Jimmie L. Lewis, 38, a 15-year-veteran of the force, was taken to the Washington Hospital Center Medstar unit by helicopter after the 6:30 p.m. shooting in the rear yard of the of the Scott Montgomery Elementary School at Fourth and P streets NW.

Early this morning, investigators said they had identified several suspects in the incident, but no charges had been filed.

Dr. Frederick Finelli, a specialist in trauma injuries at the hospital, said last night that two shots struck Lewis, one in the left side just below the rib cage and one in the thumb of his right hand.

Lt. William White III of the D.C. police department said that before the shooting Lewis and his partner, Byron Wallace, 38, both of the 1st District police vice unit, were investigating area residents' complaints of drug dealing in the area.

White said the two officers went to the neighborhood after police received a tip from an anonymous caller who indicated that a drug transaction would be made in the area last night.

While there, the two officers apparently made a drug purchase as part of the investigation, a police official said.

As the officers identified themselves, White said, one of the suspects produced a gun and fired an undetermined number of shots at the officers. As the suspects turned and fled, the officers returned the fire and chased them for a short distance, White said.

The site of the shooting is about 50 yards from the nearest house. Residents of the area who were interviewed last night indicated that they neither saw nor heard anything unusual at the time of the shooting.

White said neither of the officers was wearing a bulletproof vest when the shooting occurred.

"We are still in the preliminary stages of the investigation, but it appears as though he Lewis was not wearing a vest," White said.

The D.C. police department does not require its officers to wear bulletproof vests, but the vests are made available to officers who desire to wear them, White said.

Finelli said last night that the bullet that hit Lewis in the left side "came out the middle of his back but missed his spinal cord and most of the the vital organs." He added that the wound to the officer's hand was minor and that Lewis' chances of recovery were good.

The last officer to be shot in the District was Sgt. Joseph Cournoyer, 30, of the 6th Police District. Cournoyer, a six-year member of the force, was shot and killed while attempting to remove an armed robbery suspect from a crowded bus near the Minnesota Avenue Metro station on Jan. 29.