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The international swimming federation says its executive director has been ordered to testify as a witness in a U.S. criminal investigation into the case of 23 Chinese swimmers who tested positive for a banned substance in 2021 yet were allowed to continue competing.

Swimming's world governing body, World Aquatics, told The Associated Press on Thursday that its top administrator, Brent Nowicki, was subpoenaed to testify in the investigation.

"World Aquatics can confirm that its executive director, Brent Nowicki, was served with a witness subpoena by the United States government," World Aquatics said in a statement to the AP. "He is working to schedule a meeting with the government, which, in all likelihood will obviate the need for testimony before a Grand Jury."

World Aquatics declined to answer questions about where and when Nowicki was served his subpoena and didn't say which office was handling the investigation. The FBI did not immediately return requests for comment.

The news comes just three weeks before the Paris Olympics, where 11 of the Chinese swimmers who tested positive for a banned heart medication three years ago are set to compete.

The swimmers in question were allowed to compete at the Tokyo Olympics despite their positive tests just months before those Games. Chinese officials blamed food contamination; the World Anti-Doping Agency accepted that explanation and has since defended its handling of the case.

China won six medals in swimming, including three golds, at the Tokyo Olympics to finish fourth on the medal table behind the United States, Australia and Britain.

The positive tests were not publicly known until The New York Times and German broadcaster ARD first reported on the case in April.

A House Committee on China asked the Justice Department and FBI on May 21 to investigate the case under a federal law that allows investigations into suspected doping conspiracies even if they occurred outside the U.S.

Information from Reuters was used in this report.