Investigators added that during his last year the 19-year-old player suffered from myocarditis, a condition where not enough blood gets to the heart, and should not have been playing professional hockey.
Russia's federal Investigative Committee said experts concluded from analysis of blood and urine samples that for several months Cherepanov "engaged in blood doping." There was no elaboration in the statement, and a spokeswoman at the committee refused further comment.
The committee said the club's medical team may carry legal liability, contending a "row of gross violations was committed by the medical brigade" helping Cherepanov.
"Among them, doctors arrived on the scene a full 12 minutes after Cherepanov collapsed, and the battery on the defibrillator to attempt shock Cherepanov's heart back into life was drained," the statement said.
Prosecutors this month accused the club's director of negligence. Mikhail Denisov has since been fired, and Monday's statement did not mention him.