The global anti-doping regulator disclosed Tuesday that it is investigating why athletes in China and other countries who are testing positive for banned drugs are escaping discipline through claims that they have unwittingly ingested the performance-enhancing substances through food.

The statement from the World Anti-Doping Agency (WADA) came after The New York Times reported earlier Tuesday on a previously undisclosed case in which two elite Chinese swimmers who tested positive for a powerful steroid in 2022 were cleared late last year after their country’s anti-doping authority blamed contaminated hamburgers.

It was the third incident in recent years in which China blamed food contamination for positive tests among members of its national swimming team.