BALTIMORE (AP) _ A 17-year-old high school basketball player collapsed in the locker room during halftime and was pronounced dead about an hour later, authorities said.

Jonathan Ausby III, a 6-foot-3 senior at Andover High School, had no history of heart trouble and appeared fine after scoring a game-high 15 points in the first half of Tuesday's game against Brooklyn Park High School here.

''His heart stopped and we couldn't get it started,'' said Andover Coach Dick Hart. ''I don't known what happened.''

Ausby was pronounced dead at South Baltimore General Hospital, said Dr. Joseph Grant. The medical examiner's report on the cause of death was expected today.

Grant said the death could have been caused by Marfan's syndrome, a fatal condition he said often strikes tall young athletes. The condition causes a large blood vessel in the heart to rupture after physical exertion.

University of Maryland basketball players Owen Brown and Chris Patton died of Marfan's syndrome in the late 1970s.

Teammate Stephen Beard said Ausby was breathing heavily when he came into the locker room, but did not seem ill.

''He was leaning back, supporting himself (against a locker), and he just fell back and hit his head,'' said Beard, 18.

Team manager Kerri Mattes said Hart ''got all the players in a huddle and then all of a sudden, everybody just busted out crying.''

The game continued after a 45-minute delay. Brooklyn Park won 54-53.