A Prince George's County grand jury began the major part of its investigation into the death of University of Maryland basketball star Len Bias yesterday by hearing testimony from police detectives, hospital personnel and Maryland's chief medical examiner.

The confidential proceedings concerning evidence related to Bias' death June 19 from cocaine intoxication lasted about five hours. They included testimony from Michael Ferriter, the county police homicide detective who has led the investigation, and Karl Schallhorn, the university police officer who found about 12 grams of cocaine in Bias' leased Nissan 300ZX the day after the 22-year-old all-America player died, according to sources familiar with the case.

The 23-member panel also heard from county police evidence technicians who hauled two large trash bags filled with clanging glass bottles into the large courtroom that Prince George's County State's Attorney Arthur A. Marshall Jr. is using as a grand jury room.

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 who were using it with him before he died.

Investigators have said that players Terry Long and David Gregg, along with Brian Lee Tribble, who is a friend of Bias' and a former Maryland student, were with Bias when he collapsed about 6:30 a.m. June 19. Marshall has said "evidence will show" that Tribble brought drugs into the dormitory room.

Dr. John Smialek, the state's chief medical examiner, said after leaving the grand jury that he told the panel there was no medical evidence to suggest that Bias had freebased the cocaine, a process in which the drug is purified and smoked.

Dr. Stephen Gevas, who treated Bias at Leland Memorial Hospital in Riverdale, where the athlete was pronounced dead, said that he testified about emergency procedures used in an attempt to revive Bias. Margie Jacobs, assistant director of hospital records, said she explained to the grand jury that Bias' laboratory records were filed under a different name for reasons of privacy.

The grand jury is expected to hear testimony today from Bias' friends and some teammates, including Jeff Baxter, who shared the dormitory suite with Bias and with Long, Gregg, Phil Nevin and Keith Gatlin.

Tony Massenberg, a freshman who was suspended from the team for one year for cheating on an exam, said he will go before the grand jury on Thursday.

Long and Gregg have been subpoenaed. Marshall has said that if they are called to testify, it will not be until the end of the week.

Staff writers Sally Jenkins and Susan Schmidt contributed to this report.