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. A federal official says these masks are giving first responders “a false sense of security.” Nearly a year into the pandemic, fraud remains a major problem as scammers seek to exploit hospitals and desperate and weary Americans. These schemes deliver phony products, unlike fraud earlier in the pandemic that focused more on fleecing customers.