Posted with permission from dpa German Press Agency

London (dpa) - Maria Sharapova could be about to benefit from a scientific lifeline after doubts emerged on Wednesday about the chemical properties and actions of the controversial medicine meldonium.

The marquee player of the WTA revealed six weeks ago that she had tested positive during January's Australian Open for the medicine, which was only banned by the international anti-doping agency WADA from January 1. She was then suspended from the sport with immediate effect.

Now, anti-doping officials admit that a partial amnesty for scores of athletes - mainly Russian - who have suddenly tested positive for the substance may come to pass.

The London-based International Tennis Federation would make no comment on Wednesday, citing confidentiality.

But reports indicate that researchers are no longer crystal-clear about how long Latvia-developed meldonium - a heart medication - actually stays in the body.

That technicality could eventually be enough to see five-time grand slam winner Sharapova back on court later in the season.

Sharapova was among 172 athletes who have tested positive for the substance. WADA said in a statement says that "a finding of no fault or negligence" could now be made in certain circumstances.

The sharp reversal of policy reveals that scientists remain at a loss over how long it takes meldonium to exit the body through urine (weeks or months).

Sharapova, the highest earning woman in all of sport, produced very low levels of the substance, which she said she had taken for a decade under strict medical supervision and on order of her personal physician.

London's Daily Telegraph has quoted the player's lawyer as saying that dosage level issue could form a part of the defence effort.

Sharapova is due a hearing with no date yet made public; it is believed that it will be held before the end of this month.

WADA will allow a concentration of under 1 microgram of meldonium per millilitre in test samples collected before March 1, with concentrations of up to 15 micrograms in the period up for further review, just as concentrations of less than 1 microgram in tests carried out after March 1.

Trace amounts could still be present if the athlete stopped taking the drug before it was banned on January 1, the report said.

On Friday, Russia's sport minister Vitaly Mutko threatened to take legal action against the WADA if it did not provide a grace period for Russian athletes who used meldonium before it was banned.

Mutko told reporters that traces of meldonium can remain in a user's body for up to a year. WADA informed athletes last autumn that the substance would be added to the prohibited list.

ITF boss Dave Haggary also took a swing at WADA's procedure, telling media:

"The fact that WADA felt compelled to issue this unusual statement now is proof of how poorly they handled issues relating to meldonium in 2015," he said.

"Given the fact that scores of athletes have tested positive for taking what previously was a legal product, it's clear WADA did not handle this properly last year and they're trying to make up for it now.

"The notice underscores why so many legitimate questions have been raised concerning WADA's process in banning meldonium as well as the manner in which they notified players. This notice should have been widely distributed in 2015, when it would have made a difference in the lives of many athletes."