LONDON -- Four American track and field athletes have tested positive for the designer steroid THG in their backup B urine samples taken in June at the U.S. National championships in Stanford, Calif.

The International Association of Athletics Federations, the sport's world governing body, confirmed the results Wednesday but said it did not know the identity of the four. The four, who are entitled to a hearing before the U.S. Anti-doping Agency, face a possible two-year ban.

"We can now confirm all four are positive," Istvan Gyulai, general secretary of the IAAF, told The Associated Press. "They are entitled to a hearing before American authorities and have three months from the [second] test to have it."

Gyulai also pressed American officials to name the four athletes.

"This is the only country at the moment which doesn't give us the names right after the A [samples]," he said. "All the others provide the names. This little issue is still to be brought into line with IAAF regulations."

Several media reports in the last month have named runner Regina Jacobs, shot putter Kevin Toth and hammer thrower John McEwen as three U.S. athletes who had their A samples test positive for THG, but there is no confirmation that these are the athletes whose backup samples have tested positive.

A fifth athlete, British sprinter Dwain Chambers, has recorded positive A and B results for THG, or tetrahydrogestrinone, after an out-of-competition test in August in Germany. Chambers was suspended earlier this month by UK Athletics.

The appearance of THG, which was uncovered last summer following a tip by an anonymous coach to the U.S. Anti-Doping Agency, threatens to become the biggest doping scandal in track and field history.

The UCLA doping control laboratory identified the compound as a new steroid modified to evade detection and devised a test for it.

The IAAF said earlier this week that athletes who tested positive for THG could get reduced bans if they provide information on others involved in a doping conspiracy.

The IAAF has begun retesting 400 samples for THG from the World Championships in Paris in August. Positive findings would result in retroactive disqualification, including stripping of any medals and two-year bans.

The International Olympic Committee will decide by early next month whether to test urine samples from the 2002 Salt Lake City Olympics for THG.

IOC medical director Patrick Schamasch said the organization was still considering various legal and scientific issues before making a decision at the Dec. 4-5 meeting of its executive board in Lausanne, Switzerland.