Wimbledon champion and world doubles No 1 Robert Farah is one of two leading players to test positive for steroids, the Tennis Anti-Doping Programme has confirmed.
The Colombian, who also won last year's US Open title with partner Juan Sebastian Cabal, has been provisionally suspended after providing a positive sample for boldenone in an out-of-competition test in October.
Meanwhile, Chilean world No 78 Nicolas Jarry has also been provisionally suspended after returning a positive sample for stanozolol and ligandrol during the Davis Cup in Madrid in November.
Both players blamed cross-contamination in respective statements that each posted on their social media accounts.
Farah described the news as "the saddest moment of my life", and claimed the adverse test could be due to eating contaminated meat.
"This substance is frequently found in Colombian meat and can affect the results of tests to athletes," wrote Farah. "I am sure that this condition in what generated the result of the test in question."
Farah had withdrawn from the Australian Open earlier on Tuesday, for what tournament organisers initially described as "personal reasons". Cabal is not implicated and is free to compete with a new partner.
Jarry blamed multi-vitamins he claimed to have taken in Brazil on the advice of a doctor who had "guaranteed" that they were free from banned substances.
Jarry wrote: "I would like to you know that I have never deliberately or intentionally taken any banned substance in my career as a tennis player and in fact, I am completely opposed to doping."
Jarry, who was knocked out of Australian Open qualifying on Sunday, promised his "full co-operation" to the International Tennis Federation as he awaits a full hearing.