Double Olympic champion Mo Farah missed two drugs tests in the build up to the 2012 Games, it has been reported.
The Daily Mail claimed Farah, who won gold in the 5,000 and 10,000 metres in London, missed his first test early in 2010 with another the following year. A third missed appointment could have resulted in a four-year ban.
The 32-year-old is currently in the spotlight in the wake of doping allegations made by the BBC's Panorama programme against his coach Alberto Salazar and training partner Galen Rupp.
Both men have denied the claims. The documentary made no suggestion that middle distance runner Farah has been involved in doping.
The first missed test took place before Farah was working with Salazar with the second allegedly being in February 2011, after the double world champion became part of the Nike Oregon Project in Portland, according to the Daily Mail.
Farah claimed he did not hear the doorbell when missing his second test and that his agent Ricky Simms submitted video evidence to back up that defence, the newspaper reported.
Salazar is then quoted as telling Farah in May 2011: "If you miss another test, they will hang you."
The report then publishes e-mails apparently exchanged between UK Anti-Doping's lawyers and Farah's representatives in which the lawyers say: "Intent and negligence are not the same thing, though, as I am sure you have advised him.
"The simple fact with this Missed Test is that your client says that he did not intend to miss the test, but it is clearly his own fault that he did."
Farah announced on Wednesday he would return to the track for the first time since the doping allegations against Salazar emerged at the Monaco Diamond League meeting on July 17.
He pulled out of the Sainsbury's Birmingham Grand Prix earlier this month, stating he was "physically and emotionally drained" by the affair.
Rather than racing in Birmingham, the 32-year-old jetted back to his Portland home to seek answers from Salazar.
On Wednesday he was back on the other side of the Atlantic, posting on Twitter a picture of himself training in France.
He said: "Good to be out on the track in France today, getting ready for my next race in Monaco!! Focusing on my training!!!!"
A week after competing at the Herculis meeting in Monaco, Farah is due to race at the Sainsbury's Anniversary Games at the Olympic Stadium.
UK Anti-Doping (UKAD) refused to comment on allegations of the missed drugs tests, saying: "UK Anti-Doping does not disclose personal data relating to an individual's test history.
"UKAD has a dedicated Athlete Support Officer who works with athletes on the National Registered Testing Pool, and with National Governing Bodies of sport, to ensure they manage their whereabouts reporting responsibilities."
Its legal team is understood to be investigating how the email from its lawyers got into the public domain.