Marion Jones is not expected to return to action at this weekend's World Athletics Final in Stuttgart despite being likely to be cleared of a drugs violation.

On Wednesday night the American was informed by the United States Anti-Doping Agency that a "B" test for erythropoietin (EPO), a blood-boosting hormone, had tested negative. The result, forwarded to the athlete through her lawyer, contradicted that of the "A" sample which proved positive after she won the US Championships 100 metres title on 23 June.

In a statement, Jones said: "I have always maintained that I have never ever taken performance-enhancing drugs, and I am pleased that a scientific process has now demonstrated that fact. I am anxious to get back on the track."

The International Association of Athletics Federations said that it had still to be officially informed of the "B" test by either USADA or the United States Track and Field.

"For the moment we only know of the result by what we have read in the media and we have also heard nothing from the laboratory which undertook the tests," the communications director Nick Davies said. "We will not be commenting further until official notifications of the 'B' test have been received."

He confirmed that provisional start lists for this weekend's meeting in Stuttgart had already been publicised and Jones was not among the eight starters in the 100m final. That means the 30-year-old sprinter, despite her enforced lay-off, is still lying second in the IAAF world rankings which should have offered her a guaranteed lane in the race. Instead it seems Jones will lose the opportunity to chase the $30,000 (£16,000) first prize.

However, if Jones is quickly given the all-clear there is every likelihood that she will take her place in Team USA for the IAAF World Cup in Athletics next weekend in Athens.