Jacobs won the world indoor title in March

America's world indoor 1500m champion Regina Jacobs and hammer thrower John McEwen are reported to be the latest athletes to have tested positive for the steroid THG.

The Washington Post newspaper has reported that Jacobs, the first woman to run under four minutes for the 1500m indoors, is one of the four previously unnamed American athletes to test positive for THG.

The Chicago Tribune has reported that 29-year-old McEwen, who came second in the US national championships in June, is another.

Should "B" tests confirm the positive tests, the athletes face possible lifetime bans and US$100,000 fines as a result of a new zero tolerance initiative introduced by the United States Track and Field.

The news follows the revelation that British 100m runner Dwain Chambers also tested positive for the previously undetectable drug.

Jacobs raised eyebrows when she broke the 13-year-old world indoor 1500m record at the age of 39 earlier this year.

Authorities in Germany, France and Greece have confirmed they will re-test samples taken at domestic and international events this year.

USATF spokesperson Jill Geer said the tougher measures were necessary in the light of the recent developments.

The THG scandal explained

"Those of us charged with leading the organisation have an opportunity and responsibility to take swift and comprehensive action to address this problem," she said.

"The cost of creating and implementing an effective programme will be high. To the extent that we succeed by catching more cheaters, the short term pain will be significant.

"But, there is no responsible choice other than to follow this course of action."

The American athletics federation is just one of the many sporting bodies who have been handed instructions on how to detect the designer steroid.

The test for THG, developed by Professor Don Catlin at the University of California, has been forwarded to the various associations by the World Anti-Doping Agency.

"We commend the UCLA lab for moving quickly not only to identify this substance, but also for making sure the other laboratories have access to this test as quickly as possible," said Wada's director general David Howman.

"This sends a strong message that there will be no delay in catching those who cheat or who believe they can stay one step ahead of the system."

Howman also insisted international sports federations and anti-doping agencies re-test previous samples stored in laboratories for THG.

The International Association of Athletic Federations have already made clear they plan to re-test all urine samples taken at the World Championships in Paris for the previously undetectable drug.

Arne Ljungqvist, head of the International Olympic Committee's medical commission, said it was likely that more positive test results would emerge over the coming months.

"It remains to be investigated but I would not be surprised if it has been going on for a year or more," said Ljungqvist.

"Athletics is a sort of international community. There may also be some international ramifications. It would surprise me if there were not."

The doping control laboratory at UCLA developed a test for THG after an anonymous coach turned in a used syringe containing the substance to the United States Anti-Doping Agency.