Chinese Olympic and World Champion swimmer Sun Yang was banned for three months in May after failing a doping test, Chinese media has revealed.
The China Anti-Doping Agency said he had tested positive for a banned stimulant trimetazidine, state news agency Xinhua reports.
He went on to compete in the Asia Games in South Korea in September, taking three gold medals.
Sun Yang became the first Chinese male swimmer to win Olympic gold in 2012.
He took gold in the 400m and 1,500m freestyle events at London 2012.
Xinhua said Sun failed the doping test at the national swimming championships in Hangzhou, but had served his ban by the time of September's Asian Games in Incheon.
Trimetazidine has been banned by the World Anti-Doping Agency since January.
Sun is a popular sports star in China but has been in the news before for his exploits out of the pool.
Last year he was held for seven days in police detention for driving without a licence, after a Porsche jeep he was driving collided with a bus.
He also reportedly fell out with his coach over a relationship with a flight attendant.