Olympic long jump silver medallist Luvo Manyonga has been provisionally suspended for anti-doping whereabouts failures, the Athletics Integrity Unit said.
The South African has been issued with a notice of charge and could face up to two years suspension if found guilty, which would rule him out of the Olympic Games in Tokyo that are provisionally scheduled to start in July.
A Whereabouts Failure charge can be laid against an athlete for failing to submit their location ahead of time for random out-of-competition drug tests, or failing to appear at a pre-arranged time for a test three times in a 12-month period.
Manyonga was not immediately available to comment.
Manyonga's Olympic silver medal in Rio de Janeiro in 2016 was a remarkable tale of triumph over adversity, with the athlete having previously admitted recreational drug addiction.
He underwent rehabilitation and did not compete between 2012 and 2014.
Manyonga was given an 18-month suspension by the sport's world governing body in that period after testing positive for the recreational drug tik - the local South African variant of crystal methamphetamine.
After claiming Olympic silver in Brazil, he won the gold medal in the 2017 world championships and took first place at the Commonwealth Games on Australia's Gold Coast a year later.
The 30-year-old recently said he had not trained for a year amid a breakaway from his agent and did not know when he would begin his programme towards the Tokyo games.
"I'm not training and I don't know the way forward because I'm doing everything on my own, trying to fight my battles," he told South Africa's TimesLIVE website last month.
"My clothes are all over the world. I'm changing places to stay, I'm staying in (Paarl), my clothes are in PE (Port Elizabeth). I don't know what is the way forward for me."
He was in the news in May last year, when he was fined for contravening South Africa's coronavirus lockdown regulations by drinking in public.