Federal agents have seized more than 10 million fake N95 masks in recent weeks.

It’s the result of an ongoing investigation into counterfeits sold in at least five states to hospitals, medical facilities and government agencies.

Officials say the most recent seizures occurred Wednesday when Homeland Security agents intercepted hundreds of thousands of counterfeit 3M masks in an East Coast warehouse that were set to be distributed.

Investigators also notified about 6,000 potential victims in at least 12 states including hospitals, medical facilities and others who may have unknowingly purchased knockoffs, urging them to stop using the medical-grade masks.

Officials encouraged medical workers and companies to go to 3Ms website for tips on how to spot fakes.