BEIJING • Six Chinese swimmers have tested positive for drugs in recent months, state media admitted yesterday, after the World Anti-Doping Agency (Wada) said it is investigating an alleged cover-up.

Zhao Ying, Wang Lizhuo and An Jiabao tested positive for clenbuterol - a stimulant that increases aerobic capacity and speeds up body fat metabolism - last year, the Xinhua news agency cited the China Swimming Association (CSA) as saying.

None of them have competed at the Olympics or the World Championships.

Three other unnamed swimmers tested positive for hydrochlorothiazide - a diuretic that can be used to mask other performance-enhancing drugs - in January and are still awaiting hearings into their cases.

The announcement - weeks ahead of China's national championships - came after The Times of London cited whistle-blowers as saying five positive tests had been hidden to avoid a storm.

The newspaper's report was another blow to the sport's image, shortly after a possible doping scandal was revealed in Russia.

Wada said it is investigating both Beijing and Moscow for alleged cover-ups.

Xinhua reported that Zhao Jian, deputy director of China's anti-doping agency, had denied that the results had been covered up. He also insisted that Chinada had reported the six cases to Wada.

He added that the three hydrochlorothiazide cases were not made public because they were "still under investigation".

He did not explain why the three clenbuterol cases were kept secret until this week.

In a separate Xinhua report, Zhao was cited as saying: "We will release the results and punishments 20 days after the relevant associations have made their punishments."

It is not the first time Chinese swimming authorities have delayed revealing drug-test failures.

In late 2014, they said double Olympic champion and 1,500 metres world record-holder Sun Yang had served a three-month ban before returning to competition. He won three golds at the Asian Games months after the suspension - for the banned stimulant trimetazidine. But his ban was revealed only after the quadrennial Asiad.

Wada threatened to appeal to the Court of Arbitration for Sport over the incident. The World Anti-Doping Code says drug violations must be made public within 20 days.

AGENCE FRANCE-PRESSE