Adidas AG has suspended its contract with Tyson Gay after the former double world sprint champion failed an out-of-competition dope test, the German sportswear company said on Monday.
"We are shocked by these recent allegations, and even if we presume his innocence until proven otherwise, our contract with Tyson is currently suspended," an Adidas spokesman said.
Adidas' agreements with athletes give it the right to terminate the contract "if the athlete is found guilty of the possession or use of drugs or any other prohibited substance by the relevant governing sports body having jurisdiction over the athlete."
Gay, who has been on Adidas' books since 2005, had said on Sunday he had tested positive for a substance he could not identify and that he was pulling out of next month's world championships in Moscow.
"I don't have a sabotage story. I don't have lies ... I basically put my trust in someone and I was let down," the American said, adding that he had never knowingly taken a performance-enhancing drug.
Also on Sunday, former world 100 meters record holder Asafa Powell and Olympic 4x100 meters relay silver medalist Sherone Simpson said they had both tested positive for the stimulant oxilophrine at last month's Jamaican championships.
Powell and Simpson, both from Jamaica, have denied knowingly taking a banned substance.
The doping cases are a blow to the image of athletics a month ahead of the world championships in Moscow. The sport often struggles to maintain a high profile outside Olympic years.
German company Puma SE, which sponsors Jamaican athletics through a contract with the national association there, declined to comment because it does not have individual contracts with any of the athletes involved.
Puma does sponsor Olympic sprint champion Usain Bolt, whose manager said he was not involved in the latest doping scandal.
Chinese sporting goods company Li Ning, which sponsors Powell, was not immediately available for comment.
