Nairobi - Kenyan marathon runner Rita Jeptoo has been implicated in illegal doping dating back more than three years, according to her estranged husband and legal documents.
The allegations of possible long-term EPO use come a week after it emerged that Jeptoo, aged 33 and seen as currently the world's best female marathoner, had failed an out-of-competition drugs test carried out in September, weeks before her most recent victory in the Chicago marathon.
Jeptoo has denied being a cheat and has requested that her B sample now be tested according to procedure - although if it too is positive she faces a lengthy suspension and being stripped of her most recent titles.
Jeptoo, a three-time winner of the Boston marathon and a two-time champion in Chicago, is the biggest name in Kenyan athletics ever to have been tested positive and the news has stunned Kenya, whose naturally-gifted distance runners are an immense source of national pride.
But Jeptoo's estranged husband, Noah Busienei, has produced written allegations of Jeptoo's doping dating back to early last year, when the two were going through acrimonious legal proceedings following their separation.
According to an April 2013 letter from his lawyer to Jeptoo, Busienei had "knowledge that... you resorted to use unrecommended or banned drug hormone which increases the red blood counts."
The letter also told Jeptoo that unless she offered a financial settlement to Busienei, "he is willing to take the necessary step by revealing/disclosing/unleashing the doping dossier" to Athletics Kenya and the World Anti-Doping Agency (WADA).
Contacted by AFP, Busienei's lawyer Rioba Omboto, who is based in the Rift Valley town of Eldoret in western Kenya, confirmed the authenticity and date of the letter - written before Jeptoo's consecutive Boston and Chicago marathon victories.
Jeptoo could not be reached for comment, and has refused to speak to the media since news of the positive test was made public.
"I feel very bad for what has happened to Rita but I saw it coming," Busienei told AFP.
He said he believed Jeptoo began doping in September 2011, allegedly following advice from a foreign agent who had promised to make the couple "very rich".
Athletics Kenya revealed last week that it had been informed by the International Association of Athletics Federations (IAAF) that a sample of Jeptoo's urine had tested positive for EPO, and promised "very drastic action" if Jeptoo is confirmed as a cheat.
The organisers of the World Marathon Majors (WMM) - the series of marathons in Berlin, Boston, Chicago, London, New York and Tokyo - also postponed the awarding of this year's $500 000 prize to Jeptoo. She had been due to attend the New York marathon last weekend to collect the prize, the biggest payout in distance running.
Kenya has been under pressure from WADA to take action over doping after a string of positive tests in recent years.
But a report from an independent task-force released this year did not uncover any evidence of the use of drugs among top athletes, and insisted that "the few reported cases were aided and abetted by professional doctors, managers and agents".