Olympic lawyers are probing the legality of re-testing the samples and the IOC is also seeking scientific advice on whether the frozen 19-month-old samples remain viable.

The IOC wants to be sure the quality of the samples is still good so that there can be no question of legal issues regarding potential degradation.

"We are looking at all the criteria... all the elements, so that if we go ahead we have all the information needed," an Olympic spokesman said from the IOC's headquarters in Lausanne.

"We are certainly looking at the possibility."

The designer steroid tetrahydrogestrinone (THG) is at the centre of a growing doping scandal.

The discovery of the drug has rocked track and field in Europe and north America and could leave next year's Athens Olympics missing a host of banned big-name athletes.

Four U.S. athletes have tested positive for THG, American officials have said, as has European 100 metres champion Dwain Chambers.

The Briton said through his lawyer that if he did take the drug, it was unwittingly.

RE-TEST SAMPLES

Athletics' global ruling body, the IAAF, said last week it would re-test samples taken at August's world championships in Paris to look for THG.

The world swimming federation FINA said on Wednesday that samples taken during July's world championships in Barcelona could be tested again for THG.

"FINA continues to study with its experts the evolution of tetrahydrogestrinone... and is checking the availability of the IOC laboratory in Barcelona to perform the THG analysis," FINA said in a statement.

"If the conclusion of the FINA experts will lead to the necessity of conducting tests for THG, FINA will proceed analysing samples from the world championships held last July in Barcelona."

However, world soccer's governing body FIFA has ruled out retrospective tests for THG.

FIFA cited legal reasons and said samples are destroyed after 30 days in accordance with FIFA's doping control regulations.

Details of how to detect THG, a steroid tweaked by chemists to evade detection under normal test conditions, have been distributed to 30 International Olympic Committee (IOC) accredited laboratories worldwide and a number of national federations have committed to re-testing stored samples.

TWEAKED VERSION

Anti-doping chiefs are calling for all international sports federations to analyse currently stored samples for THG.

The World Anti-Doping Agency (WADA) has written to all the federations in a bid to close the net around drug cheats.

Don Catlin, who heads the Olympic drug-testing laboratory at UCLA, where the Salt Lake Winter Games samples are stored, told the IOC that between 200 and 300 of about 700 samples from the Games still exist and could be retested for the previously undetectable drug.

"I said, 'Yes, I have them, and yes, they can be retested,'" Catlin told the Salt Lake Tribune newspaper.

Catlin, whose laboratory performed all drug-testing at the Salt Lake Olympics, was asked to develop the test for THG after an unidentified track coach sent a syringe of the substance to the U.S. Anti-Doping Agency.

After weeks of effort, the UCLA lab found a way to detect THG, a tweaked version of two previously banned anabolic steroids.