China's national anti-doping agency hit back Monday at a New York Times article that said three Chinese swimmers implicated in a doping scandal had been involved in earlier cases, calling the story "a violation of the media ethics and morals".

The New York Times reported on Friday that three Chinese swimmers among 23 involved in a drug scandal ahead of the Tokyo Olympics had tested positive for banned substances in separate cases several years earlier.

The American newspaper said the three athletes -- including two 2021 Olympic gold medallists and a current world record holder -- tested positive for clenbuterol in 2016 and 2017.

Chinese authorities had argued the three athletes had ingested the substance inadvertently through contaminated meat, and no disciplinary action was taken, according to the report.

In a statement to AFP on Monday, China's anti-doping body hit back at the allegations.

"We have noticed the unauthorized disclosure of unpublished documents and information, and the privacy of the athletes (including minors) by media like the New York Times," the China Anti-Doping Agency (CHINADA) said.

It added that the Times "misinterpreted the positive findings for clenbuterol caused by meat contamination as intentional doping by the athletes".

"This is a violation of the media ethics and morals, an attempt to mislead public understanding on anti-doping work and caused a severe damage on the reputation of WADA, CHINADA and the global anti-doping system," the agency said.

"CHINADA deplores and rejects this, and reserves its right to take legal action as appropriate against the New York Times and other media for their reports and statements that are contrary to basic facts."

The World Anti-Doping Agency (WADA) said in a statement Friday that the three athletes in question were found to have levels of clenbuterol that were between "six and 50 times lower" than the minimum reporting level currently used by the agency.