The revelation that 23 Chinese swimmers tested positive for a banned drug seven months before the Tokyo Olympics but were secretly cleared and allowed to continue competing has exposed a bitter and at times deeply personal rift inside the sport, and brought new criticism of the global authority that oversees drug testing.

A New York Times investigation uncovered previously unreported details of the 2021 episode, in which a contingent of Chinese swimmers, including nearly half of the team that China sent to the Tokyo Games, tested positive for a banned prescription heart medicine that can help athletes increase stamina and reduce recovery times.

Within hours, the disclosure of an incident that had been a secret for more than three years had drawn strong reactions from athletes, coaches and others in the fight to keep drugs out of elite sports.