The Prince George's County grand jury investigating the death of University of Maryland basketball star Len Bias heard testimony yesterday from teammates and friends of Bias, including a D.C. police officer who was questioned about Brian Lee Tribble, one of three men with Bias when he collapsed, a source said.

The officer, Johnnie B. Walker, a longtime friend of Bias', also was asked about 12 grams of cocaine found in Bias' car the day after he died of cocaine intoxication, the source said.

County police investigators have said Bias' parents asked Walker to go to Bias' College Park dormitory room in the hours after he died on June 19 to retrieve personal belongings. Prince George's State's Attorney Arthur A. Marshall Jr. has said that Walker is not suspected of wrongdoing.

Walker also was asked yesterday how he knew Tribble, according to the source. Walker said he had met him through Bias, the source said.

Tribble, a friend of Bias' and a former Maryland student, was with Bias when he collapsed in his dormitory suite about 6:30 a.m. on June 19, police have said. Marshall said "evidence will show" that Tribble supplied the drugs to Bias.

Also testifying yesterday was Christina Johnson, a 25-year-old Washington woman who said in an interview last month that she met Bias at a convenience store on Rte. 1 in College Park at about 3:45 a.m. on June 19. Johnson said she met Bias after he called her saying he wanted to talk. They spent about 30 minutes together, she said.

Johnson has said that Bias asked her to go to his dormitory room that morning, but that she refused and returned to her home in Northwest Washington. Victor Houlon, an attorney whom Johnson hired after arriving at the courthouse yesterday, said he assumed her 30-minute testimony before the grand jury included the same information.

The grand jury, in its longest daily session since it began its proceedings on Monday, also heard testimony from Maryland basketball players Jeff Baxter and Keith Gatlin, who shared the dormitory suite with Bias and players Terry Long, David Gregg and Phil Nevin.

Baxter, Gatlin and Nevin have told police they were asleep in their rooms by about 3 a.m. and woke to find paramedics trying to revive Bias. Nevin testified on Tuesday for about an hour, his attorney said yesterday.

Julie Walker and Gail Diamond, two women whose apartment in Bladensburg was burglarized about 8 a.m. on June 19 also appeared yesterday. Police sources said that a safe belonging to Tribble was taken in the burglary. Sources have said that Walker is Tribble's girlfriend.

A Maryland State Police trooper who told county police that Tribble entered the Bladensburg apartment about 10 a.m. while the trooper was checking for evidence also appeared before the grand jury. It was not known whether the two women or the trooper testified yesterday.

Mark Fobbs, Tribble's roommate at his apartment on Cherry Hill Road in College Park, and Ron Thomas, a friend of Fobbs', also appeared before the grand jury yesterday, as did four county emergency medical technicians who responded to Tribble's call for help.

The grand jury focused some of its questions yesterday on how cocaine got into Bias' car, according to sources. University police searched the leased Nissan 300ZX sports car and found the cocaine in a clear plastic bag beneath the dashboard on the passenger side and small crystals of cocaine on the floor.

Baxter and Tribble drove Bias' car to Leland Memorial Hospital in Riverdale the morning of Bias' death, police sources said. Walker got the car keys from Baxter when Walker went to the campus to retrieve Bias' belongings, sources said, but they were unsure whether Walker drove the car.

Not all of the 19 witnesses called to testify yesterday appeared before the grand jury. The grand jury meets in secret to protect the privacy of witnesses.

The grand jury is trying to determine whether criminal indictments for possession of drugs will be issued against any persons who supplied cocaine to Bias or were using it with him before he died.

Maryland Athletic Director Dick Dull is expected to appear before the grand jury at 12:30 p.m. today. Also expected to appear today are current assistant basketball coaches Ron Bradley and Oliver Purnell and former assistant coach Bart Bellairs.

Staff writer Susan Schmidt contributed to this report.