A 15-year-old District youth hanged himself with a sheet at the Cedar Knoll juvenile detention center near Laurel yesterday, two days before a scheduled court hearing on a felony charge, authorities said.

In separate incidents, five other youths escaped from the center from Thursday to late Saturday, bringing to 37 the number of reported escapes since March.

Cedar Knoll is the annex to Oak Hill, the minimum- and maximum-security youth detention center operated by the District on a 20-acre complex west of the Baltimore-Washington Parkway near Laurel. The center has been under constant pressure from the courts since 1986 to improve its suicide prevention, staffing levels and security, and it is now the focus of an investigation into allegations of physical abuse of children by staff members.

The 15-year-old, who had been in and out of the institution, returned July 10 to the minimum-security cottage at Cedar Knoll pending Tuesday's hearing.

Officials would say only that the boy had allegedly committed serious felonies.

Robert L. Little, the District's youth services administrator, said the youth was not considered a risk to himself and thus was checked about every hour by staff members.

The boy told other youths that he was worried about Tuesday's hearing and that he missed his girlfriend. He ate breakfast yesterday and said he was looking forward to seeing his brother in the afternoon, Little said.

Shortly after 9 a.m., Little said, staff members found him in his room hanging from a noose fashioned from a sheet tied to a grate in the door used by employees to check on youths. Efforts to revive him were unsuccessful, and he was pronounced dead at 9:28 a.m. U.S. Park Police, who have jurisdiction over the site because it is federal property, consider the death a suicide.

"Everyone, as far as I can determine . . . followed the procedures," Little said in reply to questions about whether staff members could have prevented the boy's death.

Before being returned to Cedar Knoll, the boy had been living in a community-based shelter, Little said. He had previously lived with an aunt. The father is dead, and his mother's residence is unknown.

On Saturday night, Little said, four teenage boys at Cedar Knoll bolted into the surrounding woods after dinner; three were still missing yesterday. The youths had been detained on drug, weapons and vehicle charges.

Early Thursday, Little said, a 16-year-old boy who had been held on drug charges broke out the air conditioner in his room and fled. By last night, he had not been caught.

Cedar Knoll, opened in 1954, has never had a fence. Oak Hill's fence has proved easy to overcome. A month ago, 17 juveniles, including two held on murder charges, escaped from Oak Hill by cutting through the fence. In 1988 and 1989, 128 youths broke out.