LEADVILLE, Colo. (AP) – An experienced mountain biker died Saturday while participating in the grueling Leadville 100 race in Colorado’s mountains.

Scott Ellis, 55, of Johnstown, Colorado, died near the end of the 100-mile, high altitude course. It’s the first death in the history of the 32-year history of the race, called the “Race Across the Sky”.

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Ellis’ Peloton-Specialized team said he apparently suffered a heart attack while competing in his favorite race, but Lake County coroner Shannon Dent would only say that he suspected natural causes in Ellis’ death. He would not elaborate and referred questions to race organizers, Life Time Fitness. A spokeswoman for company, Amy Henderson, said it would not share details of Ellis’ death out of respect for him and his family.

“The entire Leadville family is saddened by the passing of Mr. Ellis. As a 19-time participant in the Leadville 100 Mountain Bike Race, he embodied the spirit of Leadville and truly will be missed,” Life Time Fitness said in a statement.

The company noted that many cyclists stopped their races to help Ellis, who worked as an engineer for the Colorado Department of Transportation.

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The race is draws about 1,500 riders a year. Past participants have included famed bicyclists Lance Armstrong and Levi Leipheimer. Armstrong helped support other racers in this year’s competition and sent condolences via Twitter to Ellis’ family, friends and teammates.

Ellis had been leading the rebuilding of a key road damaged in Colorado’s September 2013 floods, U.S. Highway 34 through Big Thompson Canyon. “His dedication, passion and caring grace for the people of Colorado will be profoundly missed,” the Department of Transportation said in a statement.

Ellis’ death came two weeks after mountain bike racer Will Olson died after crashing in Mount Crested Butte during the Colorado stop of the Enduro World Series.

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