Two Columbia youths, being held on charges of possession of heroin, hanged themselves with bed sheets in their jail cell at the Howard County Detention Center yesterday in what police described as apparent suicides.

The young men, both patience at Springfield State Mental Hospital, where found unconscious in the same cell at 11:00 a.m., less than an hour after they had returned from a bond hearing at the Howard County Court house. Both were pronounced dead later at Howard County General Hospital.

They were identified as Stephen A. Sylvia, 18, and Harry M. poole, 20, both of Columbia. Both left suicide notes of their families, but the contents of the notes were not made public.

Sylvia and Poole were being held in a receiving cell together after a judge had ordered them jailed on bonds of $5,000 each, county spokesperson Barbara A. Heine said. A guard had checked the cell at 11 a.m., just 10 minutes before they were found hanging, without observing anything unusual.

"Correction officials were bewildered and dismayed," said Ms. Heine. "They had no indication that this would happened."

Sylvia, poole and a third man, Roger Summerville, 19, also of Columbia, were arrested Saturday night at Merryrest Court in Columbia on charges of possession of a dangerous substance, later identified as heroin.

Summerville was released Sunday after posting bond.

Poole and Sylvia had been free on a weekend pass from the Springfield Mental Hospital. Thomas Johnson, a supervisor at the hospital, said Sylvia had been a patient for about two years, and Poole had been hospitalized voluntarily six months ago. He was to have been released Tuesday.

"They were just two everyday kids. They didn't cause any trouble here," said Johnson. "We thought they were happy kids."