A 16-year-old high school junior died Tuesday after collapsing in a stairwell at H.D. Woodson Senior High in Northeast Washington, District school officials and police reported yesterday. The cause of death has not yet been determined, a spokesman for the D.C. medical examiner's office said.

D.C. police said the student, Cyrus Briscoe, of 4826 Hayes St. NE, was walking with classmates as school was being dismissed at 3 p.m. when he said he did not feel well and collapsed on the steps. He was taken by ambulance to D.C. General Hospital and pronounced dead there at 4:50 p.m., police said.

Janis Cromer, a spokeswoman for the schools, said the youth's family has a history of heart disease. She said he was scheduled to have medical tests during Christmas vacation.

Yesterday, Clyde Briscoe, the youth's father, said his son had complained recently of chest pains after exercise, but he said the youth appeared to be in good health. He said schoolmates told him that just before his son collapsed, he and a friend were trading body punches while "horse playing."

Cromer said officials had no report of any fighting before the youth collapsed. She said school personnel administered cardiopulmonary resuscitation and mouth-to-mouth respiration but were unable to revive him.

Briscoe said a fire department ambulance did not arrive at the school until about 25 minutes after his son collapsed. An ambulance service spokesman could not be reached to determine when an ambulance was summoned and when one arrived.

Cyrus Briscoe was born in the District and had attended public schools here since kindergarten. His father said he was active in youth programs at the Capital View Baptist Church, Division Avenue and Ames Street NE.