Athletics: The US Olympic team last night found itself engulfed in the biggest doping scandal in history, one that is threatening to ruin the reputations of some of the world's best-known competitors and cast a long, dark cloud over the games in Athens this summer.

Athletics has been warned to brace itself for the release of even more damaging revelations after the disgraced American sprinter, Kelli White, said she would turn whistleblower to help anti-doping officials catch the team-mates she believes also used drugs.

It is estimated that up to a dozen leading Americans may ultimately be banned and prevented from representing their country in Athens.

So concerned are government officials that White may suffer reprisals that they have offered her round-the-clock protection if she wants it.

"The US attorney's office has informed us they consider this a very serious matter, and will respond immediately if her safety is threatened or compromised in any way," said Jerrold Colton, her lawyer.

The news that White had been suspended for two years and stripped of her 100 and 200 metres world championship gold medals she won in Paris last August after admitting using banned drugs to the US anti-doping agency has sent shudders through the athletics community.

In the first case of its kind, White (27), was suspended without first testing positive. Normally an athlete is only banned after providing a urine or blood sample analysis that is discovered to include traces of a banned substance.

But White admitted using steroids and a blood-boosting agent, EPO, after being confronted with documents that proved she had been using drugs.

Evidence of White's drug use was obtained, in part, by the US anti-doping agency from documents turned over by the Senate commerce committee after an investigation by the US justice department into the San Francisco-based Bay Area Laboratory Co-operative (Balco).

Balco is allegedly the laboratory that provided a banned designer anabolic steroid that led to Britain's Dwain Chambers, the European 100 metres champion and record holder, testing positive last August and incurring a two-year suspension.

As part of the US investigation into Balco, several prominent Olympians, including White, Marion Jones, the winner of a record five medals in the 2000 Sydney Olympics, including three gold, and her partner, the 100 metre world record holder Tim Montgomery, were among those to testify before a federal grand jury in November.

Jones and Montgomery have repeatedly denied using banned substances and Jones has threatened to sue if an attempt is made to keep her out of the Olympics without a failed drug test.

Jones has contacted anti-doping agency officials asking them to test all her recent blood or urine samples in an effort to clear her name after Conte allegedly told US government officials she was among several athletes he had provided with steroids.

"The corrosive air of suspicion and frenzied anticipation which now surrounds my client can only be dispelled through quick and decisive action," said her lawyer, Joseph Burton.

Burton also said Jones would like to meet anti-doping agency officials, but was keen to emphasise that this should not be interpreted to mean she was entering into negotiations with the agency.