COLORADO SPRINGS, Colo. -- Swimming's world governing body will retest hundreds of athletes' urine samples from this summer's world championships for the new designer steroid THG.

World Anti-Doping Agency director general David Howman said FINA's decision and Rugby's plans to test athletes at its World Cup could lead several sports to follow suit.

"We have encouraged those who have collected samples over the last period of time to test for this particular substance," Howman said. "We expect a rolling continuation of that throughout sports."

Howman was part of 30 officials from international anti-doping agencies, sports federations, drug labs and athletes that took part in a two-day anti-doping symposium.

The group gathered to talk about standards for testing athletes out of competition, but the recent discovery of THG was certainly on everyone's minds.

U.S. Anti-Doping Agency officials uncovered THG, or tetrahydrogestrinone, after an unidentified coach sent a syringe he says came from Bay Area Laboratory Co-Operative in California. Lab founder Victor Conte denies being the source.

Anti-doping officials have developed a screening process for the previously undetectable drug, putting sports organizations in a scramble to retest athletes.

Four U.S. track athletes tested positive for THG at the U.S. nationals in June, and Dwain Chambers, Europe's top sprinter, failed an out-of-competition drug test.

The NFL also is retesting football players' samples for the newly identified steroid.

Howman said his organization has not seen numbers or names of athletes that have tested positive for THG, but he wouldn't be surprised if more surface.

"We are waiting for the process to take place, but we have a funny suspicion that there may be more that are going to come out of the woodwork," he said. "I'm sure there are some athletes out there that have their fingers crossed very tightly."

The new drug has plenty of people worried.

The Food and Drug Administration ruled Tuesday that THG was derived from another steroid and designated it as an illegal drug.

Legislation was introduced in the Senate last week that will give the FDA broader powers over dietary supplements to prevent drugs like THG from sneaking onto the market.

USADA officials also are working on ways to prevent others from circumventing the system.

"We have a pretty good idea of where people might be going with new kinds of designer drugs and where they might be getting the information with that," USADA general counsel Rich Young said. "We're going down that trail right now."

But to do that, Howman said, anti-doping organizations will have to rethink their approach to the screening process.

"You have to get into the mind of a scientist who is designing something specifically to cheat, which is quite a lot different from the scientist in the past who has been designing drugs to help those afflicted with illness," Howman said. "There's a mind-set change required."