WASHINGTON (AP) Federal authorities are investigating a massive counterfeit N95 mask operation in which fake 3M masks were sold in at least five states to hospitals, medical facilities and government agencies. The foreign-made knockoffs are becoming increasingly difficult to spot and could put health care workers at grave risk for the coronavirus.

These masks are giving first responders a false sense of security, said Steve Francis, assistant director for global trade investigations with the Homeland Security Departments principal investigative arm. He added, Weve seen a lot of fraud and other illegal activity.

Officials could not name the states or the company involved because of the active investigation.

Nearly a year into the pandemic, fraud remains a major problem as scammers seek to exploit hospitals and desperate and weary Americans. Federal investigators say they have seen an increase in phony websites purporting to sell vaccines as well as fake medicine produced overseas and scams involving personal protective equipment. The schemes deliver phony products, unlike fraud earlier in the pandemic that focused more on fleecing customers.