MUNICH -- As many as 21 athletes from five sports may have been part of a doping ring stretching around the world, German prosecutors said Wednesday.
Austrian police arrested five competitors at the Nordic skiing world championships last month and the case has since spread to cycling. Munich prosecutor Kai Graeber said the scandal could spread further.
Graeber said blood doping has occurred in at least 10 different countries since late 2011 and "there is believed to have been a three-figure number of cases of blood withdrawal and re-transfusion around the world."
The athletes come from eight different countries, Graeber said.
Authorities aren't naming suspects or the sports affected, but Graeber said three of the five sports are winter events.
Graeber added that doping allegedly took place in European countries such as Italy, Sweden and Croatia, along with the U.S. state of Hawaii and last year's Olympic host South Korea.
The U.S. Anti-Doping Agency confirmed that it was investigating the Hawaii connection.
"We can confirm that we are cooperating with officials in Germany and Austria and have offered all assistance in this case," the agency said in a statement to The Associated Press.
The International Olympic Committee did not immediately respond when asked whether it feared blood doping could have compromised last year's Winter Olympics in Pyeongchang.
Since the five skiers were arrested last month shortly before a world championship race, another Estonian skier has admitted to doping and two Austrian cyclists who raced in the Tour de France have been suspended.
Five non-athletes have also been arrested in Germany and Austria, including a doctor, Mark Schmidt, who used to work in professional cycling.
Graeber said the most recent arrest was made Monday in the German city of Erfurt of a person who is suspected of transporting blood for athletes and carrying out blood transfusions. That person had no medical training and "instead learned to inject on the principle of learning by doing," Graeber said.
Austrian police earlier opened an investigation after a video was posted online by media apparently showing skier Max Hauke in the middle of a blood transfusion.
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