Prince George's County investigators have been told that University of Maryland basketball coaches knew that a member of the team was a drug user and that one player switched urine samples with another during random drug testing, State's Attorney Arthur A. Marshall Jr. said yesterday.

Marshall said a county grand jury looking into the death of basketball star Len Bias will investigate whether the cocaine that killed Bias was supplied by Brian Lee Tribble, a longtime friend who was one of three persons with Bias when he collapsed in his College Park dormitory suite June 19.

"We believe the evidence will show that Tribble brought the drugs into the room," Marshall said.

Law enforcement officials believe the cocaine Bias used came from a distributor in the Baltimore area and not from Northeast Washington, as previously suspected, sources close to the investigation said.

Investigators also are looking into allegations that a woman was in the dormitory suite with Bias, Tribble and players Terry Long and David Gregg in the hours before Bias collapsed about 6:30 a.m., the sources said.

Earlier that morning Bias was stopped three times -- once by campus police and twice by a campus security force -- for driving too fast on campus roads in his Nissan 300ZX, a source close to the investigation said. The source said Tribble was in the car with Bias when the car was stopped sometime between 1:30 and 2:07 a.m.

Investigators believe that on two of those occasions, Bias and Tribble were going to and returning from a liquor store on Rte. 1 in College Park, where an employe said Bias bought malt liquor and cognac.

Marshall began the grand jury investigation four days after Bias' death of what the state medical examiner termed "cocaine intoxication." The prosecutor said the grand jury would try to find out who supplied the drug to Bias and that the probe would also explore possible drug use among university athletes.

A source close to the basketball team said county investigators were told that Coach Lefty Driesell was informed twice during the last year that one current team member "had a drug problem."

Another member of the coaching staff also was told of the drug use, the source said.

Sources said investigators were told the player was not Bias.

Driesell declined to comment yesterday on the investigation, saying that a memo from university Chancellor John B. Slaughter asked that school officials refrain from discussing the case.

"When it's all over, I'll talk," said Driesell, who has been subpoenaed for possible grand jury testimony.

"We will be checking out these allegations," Marshall said. "The question is what came of it?"

Marshall said that investigators also were told that one player who does not use drugs had allowed another player to substitute his urine sample during random drug tests conducted by the athletic department and the university health center throughout the season.

During drug testing, athletes are sometimes allowed to go into bathroom stalls unaccompanied to provide urine samples. University officials have acknowledged that the procedures need to be changed to prevent athletes from hiding a clean urine sample in their clothing.

Investigators also have received information that team members who were notified of an impending drug test either took a diuretic to flush out their systems or put a common plumbing chemical into their urine samples to alter the test results, Marshall said.

Allegations concerning the university's athletic program will not be brought before the grand jury until Aug. 11, Assistant State's Attorney Jeffrey Harding said. During those sessions, Harding said, the grand jury will hear information concerning the drug testing program and the academic performance of the university's athletes.

Marshall, whose office has subpoenaed more than 75 potential witnesses for the grand jury, said the investigation will focus initially on Tribble, who has not been subpoenaed. Under Maryland law, persons who testify before a grand jury investigating a drug case are granted automatic immunity from prosecution on drug charges stemming from that case. Police cannot otherwise compel persons to submit to questioning.

Tribble's attorney, William Cahill Jr. of Baltimore, said he is not surprised his client is the focus of the probe. "He's the only person who has not been subpoenaed," Cahill said. "But I've never seen or read anything about why" the investigation is focusing on Tribble.

Marshall said that investigators are checking to see whether Tribble attended a basketball game last year in Raleigh, N.C., between North Carolina State University and Maryland. After the game, Bias and teammates Jeff Baxter and John Johnson were suspended for what Driesell said was missing a team curfew.

"We've been given the name of an airline to check on whether Mr. Tribble was a passenger on the date of the game," Marshall said. "It may take a while to get that information. Airlines are difficult to work with."

Marshall also said that a Raleigh police officer has been subpoenaed in case the grand jury wants to look at records from the police department there.

Tribble, Long and Gregg have refused to talk with police investigators about Bias' death. Long and Gregg, who were dorm mates of Bias, have been subpoenaed.

Marshall said that Johnnie B. Walker, a D.C. police officer who retrieved Bias' property from the dormitory suite, will be asked to testify before the grand jury but is not suspected of any wrongdoing.

Walker, who had known Bias for almost 10 years, went to the dormitory room shortly after Bias died at the request of Bias' parents, said Robert J. Matty, Walker's attorney. Robert Wagner, who coached Bias and Gregg at Northwestern High School in Hyattsville, was with Walker, police said.

Wagner, who also has been subpoenaed, said yesterday that Gregg and Long spent the night and part of the day after Bias died at his house. He said a university official whom he declined to identify asked him to put the players up.

"My assumption was that the press would be hassling them," Wagner said. Wagner said neither player told him what happened in the dormitory suite in the hours before Bias collapsed.

The day after Bias' death, campus police found about 12 grams of cocaine in Bias's leased sports car, police said.

Maryland State Police tests on the cocaine proved it to be "of a very high quality," according to a source close to the investigation. The chief medical examiner had said that the cocaine that Bias ingested was unusually pure.

However, state officials said it would difficult to say with certainty whether the cocaine that Bias ingested, the cocaine found in his car and cocaine found in a trash bin outside Bias' dormitory were the same.

Although law enforcement officials believe the cocaine that Bias used originally came from Baltimore, police are also investigating possible ties between the Bias case and people with ties to a major cocaine ring in the Washington area, sources said.

A suburban Maryland residence identified during an investigation last year as a storage place used by a convicted Washington drug dealer, Cornell M. Jones, has been linked to the Bias case, a law enforcement source said.

The source said there was no evidence connecting Jones, who is in federal prison in Leavenworth, Kan., to Bias' death. Jones, who is seeking to withdraw his guilty plea in federal court in Washington, denied any involvement in the Bias case in a petition filed this week in U.S. District Court.

Staff writers Joe Pichirallo and Sally Jenkins contributed to this report.