More than 11 million counterfeit N95 masks have been seized by the Department of Homeland Security over the past few weeks, the agency announced on Wednesday. 

In a press conference, Alejandro Mayorkas—the current Secretary of Homeland Security—said the counterfeit devices were targeting healthcare workers across the country.

“Over the last few weeks, Homeland Security Investigations—the criminal investigation arm of ICE—has seized over 11 million counterfeit N95 respirators intended to be used by frontline healthcare workers throughout the nation,” Mayorkas said. “That includes a seizure earlier today … of more than 1 million counterfeit masks as part of an ongoing investigation into a criminal enterprise distributing masks throughout the United States.”

Over the past two weeks, Mayorkas said, there have been multiple search warrants executed resulting in seizures of counterfeit masks across five different states. 3M, a leading mask manufacturer, helped in the agency’s efforts by providing leads. The counterfeit operation was “taking advantage of our fears,” Mayorkas added.

Thousands of possible victims of the fake mask scam, per a report from CBS News, have been notified by the DHS. That report also cited an initial investigations as having revealed China as a source of the fake masks, which are said to have been deigned to resemble legitimate 3M products.

“I can’t stress how important it is to ensure we have the legitimate 3M N95 masks that are being deployed to our first responders,” Steve Francis, the director of the Intellectual Property Rights Coordination Center, said.

For a list of approved N95 respirators from the CDC, click here