Olympic long jump silver medallist Luvo Manyonga has been provisionally suspended for three breaches of anti-doping rules in 12 months.
The 30-year-old South African, who has battled drug addiction in the past, could be banned for two years for the whereabouts failures.
The delayed Tokyo 2020 Olympics are scheduled to start on 23 July 2021.
Manyonga is among the favourites to win gold in Tokyo after winning the 2017 World and 2018 Commonwealth titles.
In 2012, Manyonga was banned from athletics for 18 months after testing positive for crystal meth.
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