Retired welterweight Amir Khan continues to maintain that his positive drug test last year was a complete accident.

It was revealed earlier this year that Khan, the former junior welterweight titlist from Bolton, England, tested positive for a banned performance-enhancing drug. The test was administered immediately after his sixth-round knockout loss to longtime rival Kell Brook. The drug in question was ostarine, an anabolic agent.

United Kingdom Anti-Doping slapped Khan with a backdated two-year ban, but it is mostly redundant since Khan retired after the Brook fight and has continually maintained that he has no interest in fighting again. Khan has lately been making the media rounds ahead of his forthcoming autobiography.

In a recent interview, Khan suggested a possible theory for his positive drug test: that he shared a spiked drink, possibly with one of his friends, many of whom, Khan says, are apparently into bodybuilding.

“It could have been from drinking from someone’s drink,” Khan told Boxing News. “A lot of my friends are on steroids, because they want to be big. The new thing is that everyone wants to be on steroids. I might have shared a drink with someone. But I’ve never cheated in boxing.”

Khan added in the same interview that his “flat” performance against Brook should disabuse fans that he derived any competitive advantage from a drug.

“I didn’t want to be there,” Khan said. “If I knew I was on something I’d have psyched myself up. ‘I’m on this, and I’m gonna be stronger.’

News of Khan’s positive test comes at a time when a spate of other offenders have cropped up in boxing.

Welterweight Conor Benn tested positive twice for the banned substance clomifene. More recently Dillian Whyte, Robert Helenius, Joe Cusumano, Alberto Puello, and women’s 130-pound undisputed champion Alycia Baumgardner all tested positive for at least one banned substance.

Sean Nam is the author of Murder on Federal Street: Tyrone Everett, the Black Mafia, and the Last Golden Age of Philadelphia Boxing.