Mastercard and Visa failed to stop their payment networks from laundering proceeds from child sexual abuse material and sex trafficking on the popular website OnlyFans, according to allegations in a previously undisclosed whistleblower complaint filed with the U.S. Treasury’s financial crimes unit.

The whistleblower, a senior compliance expert in the credit card and banking industries, said the two giant card companies knew their networks were being used to pay for illegal content on the porn-driven site since at least 2021, and accused them of “turning a blind eye to flows of illicit revenue.”

The complaint was filed in January 2023 with the Treasury’s Financial Crimes Enforcement Network (FinCEN) and the U.S. Justice and Homeland Security departments, the whistleblower said.