NEW YORK – Twenty-three top Chinese swimmers tested positive for the same banned substance seven months before the Tokyo Olympic Games in 2021.

But they were allowed to compete after Chinese officials secretly cleared them and the global authority in charge of policing drugs in sports chose not to intervene.

Several of the athletes who tested positive for the performance-enhancing heart drug trimetazidine – including nearly half of the Chinese swimming team at the Tokyo Games – went on to win medals, including three golds.

Many still compete for China and several, including double gold medallist Zhang Yufei, are expected to contend again in Paris 2024.

China had acknowledged the positive tests in a report by its anti-doping regulator, saying the swimmers had ingested the banned substance unwittingly and in tiny amounts, and that no action against them was warranted.

But an examination by The New York Times and reported on April 20 found that the previously unreported episode sharply divided the anti-doping world, where China’s record has long been a flashpoint.

US officials and other experts said the swimmers should have been suspended or publicly identified pending further investigation. They said the failure to do so rested with Chinese sports officials, World Aquatics and the World Anti-Doping Agency (Wada).

Those authorities decided not to act despite an e-mail exchange between a Chinese anti-doping official and a top world swimming official appearing to indicate that a violation may have taken place.

Even after other national and international anti-doping officials repeatedly provided Wada with intelligence suggesting a cover-up, the agency chose not to try to hold the athletes accountable, asserting “a lack of any credible evidence”.

Experts in anti-doping, drug-testing and compliance told the Times that the handling of the Chinese swimmers and the lack of disclosure about the positive tests ran counter to long-established precedents meant to ensure transparency, accountability and competitive fairness in elite sports.

The episode also exposes shortcomings in the system set up to police doping in sports, with one of the world’s most powerful countries able to send athletes who had recently tested positive to the world’s most high-profile competition, where they set world and Olympic records without any public disclosure.

An investigation by the Chinese anti-doping agency, Chinada, suggested that the incident stemmed from a tainted food supply from the kitchen of the hotel the swimmers were staying at, a finding that some experts considered implausible. Their report offered no evidence of how the drug got there.

Wada confirmed that it had “carefully reviewed the decision” made by the Chinese and chose not to act after consulting scientists and external legal counsel “to thoroughly test the contamination theory presented by Chinada”.

“Ultimately, we concluded that there was no concrete basis to challenge the asserted contamination,” said Olivier Rabin, Wada’s senior director of science and medicine.

World Aquatics confirmed the review by a doping control board and subjected to independent expert scrutiny, without providing further details.

“World Aquatics is confident that these AAFs were handled diligently and professionally, and in accordance with all applicable anti-doping regulations, including the World Anti-Doping Code,” it said, referring to adverse analytical findings, the term for positive tests.

Chinese swimming has a chequered doping history, with a rash of cases throughout the 1990s. Seven Chinese swimmers tested positive for steroids at the 1994 Asian Games in Hiroshima.

In 1998, swimmer Yuan Yuan was banned after Australian Customs officers discovered a large stash of human growth hormone in her bags at the World Championships in Perth.

More recently, three-gold Olympic champion Sun Yang was banned for doping, ruling him out of the Tokyo Olympics. NYTIMES, AFP