TOKYO -- A 15-year-old, 308-pound sumo has died of heart disease, the first active wrestler in the ancient Japanese sport to die in three years.

The 6-foot-2 wrestler, identified as Yoshitake Maeda, had been treated by doctors since April, a Japan Sumo Associated official told Kyodo news agency.

He died of cardiomyopathy, a problem with the muscles in the heart, the report said

Phone calls were not answered at the sumo association and the center where Maeda reportedly was training.

Maeda had passed a health exam to participate in the lower junior jonokuchi division for the spring tournament in March but was later dropped from the rankings, Kyodo said. He missed the summer tournament in May, it said.

"There were no signs of any problems with Maeda when he was examined as a new wrestler. In the future we would like to carry out stricter examinations," the association's head medical official Hiroyuki Yoshida, was quoted as saying.

The sumo association has required wrestlers to undergo medical checkups after several died of heart problems in 1992. Since then, 10 wrestlers have been ordered to retire from the ring because of health problems.