OSAKA, Japan — A doping test has come back "suspicious" at the track and field world championships, but the sport's world governing body won't reveal the source yet.

IAAF president Lamine Diack would not identify the athlete or country.

"There's one case we have doubts about," he said at a press conference today, adding he expected an announcement in a week.

IAAF spokesman Nick Davies declined to elaborate whether the test came from a medalist or if the athlete was male or female.

"It might not even end up being positive," he said. "It means something that has to be checked into; something suspicious, doubtful."

It would be the first doping violation at the 2007 world championships. Two athletes had their performances annulled at the 2005 championships in Helsinki — hammer thrower Vladislav Piskunov of Ukraine and discus thrower Neelam Jaswant Singh of India.