DETROIT (AP) — Emanuel Steward, the owner of the legendary Kronk Gym and a trainer for boxers including Thomas Hearns, Evander Holyfield and Oscar De La Hoya, died Thursday. He was 68.

Victoria Kirton, Steward’s executive assistant, said Steward died at a Chicago hospital. She did not disclose the cause of death.

Steward trained, helped train or managed some of the greatest fighters of the past 40 years out of the Kronk, a dingy, overheated basement gym that produced world champions like Hearns, Sugar Ray Leonard and Lennox Lewis.

Steward was born in West Virginia and moved at the age of 12 to Detroit. In 1963, an 18-year oldSteward, fighting as a bantamweight, won the national Golden Gloves tournament. According to a biography on his website, rather than go forward as a professional he went to work for the Detroit Edison Co. and in 1971 accepted a part-time position as head coach of the boxing program at the Kronk Recreation Center.

A dynasty was born.

The Kronk’s first professional champion was Hilmer Kenty, a lightweight from Columbus, Ohio, who started training there in 1978 and won the WBA title two years later.

It was Hearns who really put Kronk — and Steward — on the map. The Hitman was the first man to win titles in four divisions — he won five overall — and topped his 155-8 amateur record by going 61-5-1 with 48 knockouts as a pro.

“He brought the very, very best out of me,” Hearns once said of Steward.

The gym for years was seen as a way to keep kids out of trouble and off the streets in southwestern Detroit. In 2006, Detroit shut down the recreation center that houses the gym because of a major budget shortfall. The gym was allowed to remain open, but it put Steward in a difficult financial situation and he rented space at a gym in Dearborn so his young fighters could train.

Steward, who was inducted into the International Boxing Hall of Fame, also worked closely with Lewis during his title run, and current heavyweight champion Wladimir Klitschko as recently as July. Klitschko has trained recently without Steward for his fight against Mariusz Wach next month in Germany.

“His spirit is always here,” Klitschko said. “I can hear his voice in sparring while doing things, whispering in my ear. As the famous saying goes, ‘The show must go on,’ and that’s exactly the case.”

Steward also worked since 2001 as a boxing analyst for broadcaster HBO.

“Manny was a respected colleague who taught us so much not only about the sweet science but also about friendship and loyalty,” HBO Sports President Ken Hershman said. “His energy, enthusiasm and bright smile were a constant presence. Ten bells do not seem enough to mourn his passing.”