Tyson Gay's positive drugs test was "terrible" news, according to Lamine Diack, head of track and field's world governing body, the IAAF.
Gay, the second fastest sprinter ever, and Jamaican ex-world record holder Asafa Powell, the fourth fastest, were revealed as having failed doping tests last week.
"I know the two of them well, they're two great guys," said Diack. "I know Asafa well, it's a catastrophe for me.
"And to see that Tyson was positive was terrible for me because I know the boy and I had occasion to talk to him and his mother after Osaka (where the American won triple sprint gold).
"We took the same plane and spent about 10 hours together, we discussed how we see our sport, what his role is as a role model. What happened, we'll see, I'm waiting to find out."
The positive tests, Diack continued, "were really harmful to our sport, especially two at such a high level".
"This is very difficult for our sport. Someone could write a book about what's going on: is the performance really acceptable or not? But I think that's wrong.
"We're doing thousands and thousands and thousands of tests in and out of competition."
But he said the media were partly to blame: "We have 1,000 tests and 50 positives, and the 50 positives are news, the 950 negative are not news.
"We will do our best to catch the cheaters."