DETROIT — 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, 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.”