Prince George's County police investigating the death of 13-year-old Kathleen Ann Murphy said yesterday that preliminary evidence indicated the West Hyattsville girl had drowned.

The girl's nude body was found lying face down in the shallow water of Sligo Creek Wednesday morning, about one block from her home at 1709 Dayton Rd.

Lt. Richard Kollmann, commander of the police homicide bureau, said investigators are not certain the girl was murdered. He added, however, "I haven't considered the possibility that it was an accident."

State medical examiners conducting an autopsy of Murphy's body said it will be several days before the official cause of death can be determined.

Dr. Hormez Guard, who is supervising the autopsy, said there were no signs that Murphy had been beaten or raped. Chemical tests are under way that should conclusively show whether Murphy drowned and whether she was raped.

Kollmann said 15 to 20 investigators canvassed the neighborhood around the park and the girl's home yesterday, interviewing residents and searching for additional evidence.

By late yesterday, however, police reported they had no suspects or possible motives in the case, although they were still looking for a blond, teen-aged youth who was reportedly involved in several recent incidents of indecent exposure in the West Hyattsville area.

Kollmann said yesterday that police have received reports of cases of indecent exposure which occured in the park and the surrounding area the past few months, all involving a blond youth.

And the night of the murder, a neighborhood boy, Wayne Odham, told police of chasing a shirtless youth with blond hair through the park after he saw the youth following a teenaged girl.

Kollmann said police do not know whether the incidents of indecent exposure and the chase through the park are related, or if either case is connected to Murphy's death.

Kollmann said investigators have interviewed two neighborhood youths who say they saw Murphy near a bridge over Sligo Creek at the corner of 17th Street and East-West Highway, shortly after midnight Wednesday.

Previously, the last person known to have seen Murphy was a friend with whom she had been staying. She left the friend's house for her home at about 11 p.m.

The bridge where Murphy was seen is on a shortcut between her home and her friend's house, Kollmann said.