A congressional staff inquiry has found "many major and serious questions" surrounding the death of a mentally retarded young man at St. Elizabeths mental hospital last month, D.C. Del. Walter E. Fauntroy said yesterday.

Emory Lee, who had heart problems and a history of epileptic seizures, died after he was placed in a locked and hot "seclusion room" at the hospital to control his behavior.

His body temperature was 106 degrees more than an hour after his death, leading to speculation that overheating was a key factor in his death. The cause of death, however, has not yet been determined.

Fauntroy indicated that the inquiry raised doubts about whether the staff checked on Lee every 15 minutes, as required by hospital procedures, though hospital charts show that he was monitored. Hospital staff members said they gave him fluids a half hour before he was found in "acute distress," but the charts do not show this, Fauntroy said.

"I am concerned about some contradictions" in interviews and in logs recording Lee's treatment, Fauntroy said. "Perhaps some of the things on the chart were not done."

The D.C. medical examiner's office has not yet determined the cause of death because more testing was needed after Lee's autopsy, city officials said.

The D.C. police department, the hospital and the U.S. Department of Health and Human Services are conducting inquiries into the death, and Fauntroy said he would hold an investigative hearing in the spring. Fauntroy has received copies of Lee's medical records and his staff has interviewed hospital officials.

Unseasonably warm weather and an eccentric heating system combined to make the hospital buildings too hot that day, according to hospital officials.

Patients were given fluids to minimize the effect of the heat, they said.

Lee was put in a seclusion room with windows that could be opened only with a special crank that was not available to the staff on duty that evening, they said.

James Pittman, associate director at the National Institute of Mental Health, with authority over St. Elizabeths, said in an earlier interview that preliminary information "did not indicate there was any improper action or inattention" by staff, but that further conclusions would have to await the medical examiner's report.

Lee, who lived with his mother Carolyn Worthy, had been at St. Elizabeths only a few days for testing. He was about to turn 22 years old, making him legally an adult and requiring changes in his training programs.

Fauntroy, noting that St. Elizabeths is to be turned over to District government management in 1987, said he does not want the city to have to accept a facility with flawed heating, boiler and ventilation systems.