MILWAUKEE (AP) _ A teen-ager who collapsed during a basketball workout was evidently the third high school athlete this year in southeastern Wisconsin to die of undetected heart problems, health officials said Friday.

Antonio D. Stewart, 16, who played several sports at Milwaukee Trade and Technical High School, died Thursday after what a medical examiner's preliminary report called a seizure.

``I don't understand. He played sports. He played everything, football, planned to run track. After football season, he was planning to start training for a new one, wrestling,'' his mother, Yvonne Holley, said Friday.

Earlier this year, Mark Barranco, 18, of Wilmot, and Adam Lemel, 17, of Whitefish Bay, died during high school basketball games.

Stewart received a physical examination less than a year ago, Yvonne Holley said, and suggested that high schools should consider more intensive examination schedules.

Stuart Berger, medical director of the heart center at Children's Hospital of Wisconsin, said heart attacks among teen-agers are not a growing phenomenon.

``Granted our community was struck tragically with two similar heart failures of young people within the last year. It's an obviously tough issue but, I think, very honestly that, no matter what you do, some of these cases are going to go undetected,'' Berger said.

The American Heart Association says about 1 in 200,000 high school athletes die during play.