The World Anti-Doping Agency has admitted that 23 Chinese swimmers tested positive for a banned substance before the Tokyo Olympics in 2021. Many of them reportedly competed in the Games.

WADA says in a statement on Saturday that it was notified in June 2021 of a decision by the China Anti-Doping Agency to accept that the swimmers had tested positive for trimetazidine, a heart medication, earlier in the year.

The statement reveals that the Chinese agency also informed WADA that the athletes had been inadvertently exposed to the substance through contamination.

WADA says that scientists and external legal counsel thoroughly examined the report from Chinese agency.

Although WADA couldn't conduct its enquiries on the ground in China due to a COVID-related lockdown, it ultimately concluded that there was no concrete basis to challenge the assertion of inadvertent contamination.

WADA also concluded that the athletes would be held to have no fault or negligence.

An Australian media outlet reported on the doping positives on Saturday before WADA published the statement.

China's swimming team won six medals at the Tokyo Olympics, including three golds.