Olympic gold medallist Gil Roberts has been cleared of any wrongdoing and will not face a ban after an arbitrator from the American Arbitration Association (AAA) ruled he had not deliberately taken a banned substance.
Roberts, a member of the United States team which won the men's 4x400 metres relay title at last year's Olympic Games in Rio de Janeiro, tested positive for probenecid, a diuretic and masking agent, in an out-of-competition test in March.
However, the AAA has ruled that the 28-year-old from Oklahoma had "ingested a prohibited substance without fault or negligence".
The decision meant he was able to compete at the USA Track and Field National Championships in Sacramento, which served as the trials for this summer's World Athletics Championships in London.
He is set to represent the US at the event at the Olympic Stadium, which runs from August 4 to 13, as he qualified in the 400m.
Roberts' hearing following the positive test had been expedited in order to resolve the case prior to the event.
"Following an expedited hearing in order to resolve Roberts’ case before the upcoming US National Track and Field Championships, the independent arbitrator concluded that it was more likely than not that the presence of a very low concentration of probenecid in the athlete’s sample resulted from unintentional ingestion and occurred without the fault or negligence of Roberts," a statement from the United States Anti-Doping Agency read.
"As a result, Roberts will not face a period of ineligibility for his positive test, and because the sample was collected out-of-competition, no competitive results will be disqualified."
Roberts claimed the first Olympic gold medal of his career alongside team-mates Tony McQuay, Arman Hall and LaShawn Merritt in the 4x400m relay at Rio 2016.
He had previously won the event at the 2012 World Athletics Championships in Istanbul.