Sportswear manufacturer Adidas today suspended its sponsorship of American sprinter Tyson Gay for failing a doping test.
Gay, the fastest man over 100 metres this year, is waiting for results on a second sample.
Five Jamaican sprinters also tested positive for banned substances - including Asafa Powell.
Adidas AG 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.
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.
Also on Sunday, former world 100 metres record holder Asafa Powell and Olympic 4x100 metres relay silver medalist Sherone Simpson said they had both tested positive for the stimulant oxilophrine at last month's Jamaican championships.
Journalist and friend to Asafa, Leighton Levy told ITV News that he believed an explanation would surface:
Powell and Simpson, both from Jamaica, have denied knowingly taking a banned substance. The American added that he had never knowingly taken a performance-enhancing drug.