An autopsy has failed to pinpoint what...

An autopsy has failed to pinpoint what caused the death of Utah State freshman nose tackle Carleton Oats Jr., but physicians believe the athlete suffered a severe attack of acidosis that triggered a heart attack.

Oats, 18, of Oakland, Calif., was flown by medical helicopter to Salt Lake City after passing out Friday following a mile run at the Logan, Utah, school. He died of heart failure at 7:25 p.m. as doctors were preparing to perform exploratory surgery.

The autopsy and blood tests ruled out drugs as a possible cause.