The sport does not have a drug-testing policy.
"Whether it's HGH, whether it's Creatine or whether it's steroids, I know for a fact that some golfers are doing it," the nine-time major winner Wednesday told Golf Magazine, without naming names.
"I'm actually very shocked at his comments," said fellow South African Retief Goosen after a one-under-par 70 in Thursday's first round at the British Open. "I don't know what Gary was trying to prove. He might as well not have said anything."
"I think you have to name the people if you want to make it a worthy statement," Goosen later told the BBC in London.
"I know of nobody and have not heard of anyone," said Europe Ryder Cup captain Nick Faldo. "We have an official body to look into that so we will see."