WASHINGTON (NYTIMES) - Millions of counterfeit masks were bought by hospitals, medical institutions and government agencies in at least five states, and some of them were used by healthcare workers in Washington state, the federal authorities said on Wednesday (Feb 10) in announcing an investigation.

Many of the masks were clever fakes, stamped with the 3M logo and shipped in boxes that read, "Made in the USA", even though they were not made in the United States or by 3M, according to federal investigators.

Homeland Security Investigations, which is part of the Department of Homeland Security, said the fraudulent masks are dangerous because they may not offer the same level of protection against the coronavirus as legitimate N95 masks manufactured by 3M.

"We don't know if they meet the standards," said Mr Brian Weinhaus, a special agent with Homeland Security Investigations.

News of the investigation came as the Homeland Security Department's intelligence branch warned law enforcement agencies separately on Wednesday that criminals on the dark web had since December sold counterfeits of coronavirus vaccines approved by the Food and Drug Administration for "hundreds of dollars per dose".

That assessment, produced by Homeland Security's Office of Intelligence and Analysis and obtained by The New York Times, said that transnational criminal organisations in Latin America were probably best positioned to take advantage of a shortage of legitimate vaccines to distribute counterfeit and stolen vaccines, though it was unclear if they had done so.

Ms Cassie Sauer, the president and chief executive of the Washington State Hospital Association, said about two million counterfeit N95 masks may have made it into the state.

Washington state hospitals bought hundreds of thousands of the fraudulent masks, and the association itself bought 300,000 for its members, she said.

The masks were "really good fakes", Ms Sauer said, noting that they included a 3M logo, secure straps, a metal bar across the top and a foam strip across the nose.

"They look, they feel, they fit and they breathe like a 3M mask," she said.

But they were not made by 3M, she said, and officials don't know enough about them to know how protective they might be.

Many of the counterfeit masks have not been used in Washington, Ms Sauer said, noting that about 60,000 masks that the hospital association bought are still in a warehouse.

But some healthcare workers did use them before the association received bulletins from 3M and the federal government and began alerting hospitals to the fraud late on Friday, she said.

"It is incredibly disheartening - really, really frustrating to discover that we have these masks," Ms Sauer said.

"It's reprehensible, the depravity," Ms Sauer added. "We're horrified."

Ms June Altaras, senior-vice president and chief quality, safety and nursing officer at MultiCare Health System, which includes 10 hospitals in Washington, said some of the workers in its network had used the counterfeit N95 masks.

She said that officials spent last weekend collecting the counterfeits and replacing them with legitimate masks.

She said the organisation had recommended that staff members who had treated Covid-19 patients be tested for the coronavirus.

"There's a special place in the afterlife for people who would do this," Ms Altaras said, adding that the fraudulent masks had created anxiety and fear among front-line healthcare workers.

"To try to make money off of this situation is really highly frustrating," Ms Altaras said. "These clinicians have been through enough."

Coronavirus fraud has been a problem since the start of the pandemic, with unscrupulous businesses seeking to exploit the health crisis by selling fake testing kits, treatments and personal protective gear.

Law enforcement officials have seized more than 10 million counterfeit respirators and hundreds of shipments of prohibited drugs and medical supplies, according to 3M and Homeland Security Investigations.

But the counterfeit mask investigation, which was previously reported by The Associated Press, shows how these deceptive products have become increasingly sophisticated, officials said.

"We're all very careful and try to check our sources and be very wary of it," said Mr Shane McGuire, the chief executive of the Columbia County Health System in Washington.

"But the gist of it is, the easier frauds to detect have started going away, and now you're starting to see a lot a lot better construction and a lot harder to detect PPE."

Mr Weinhaus, the special agent, said that companies that claim to be medical suppliers were buying the copycat N95s, typically in China, and selling them as legitimate 3M masks.

Many of the masks include a reflective seal with the word "Peru", which 3M said it does not use outside of Latin America.

Weinhaus said the agency was trying to track the respirators back to the source and stop them at the border.

3M said that it had helped Washington, Minnesota and other states confirm that respirators that were bought from distributors with no relationship to 3M were not authentic 3M products.

While the company said that it had increased production of N95 respirators, it said it had also begun a global effort to combat fraud and price gouging.

"As part of that effort, 3M is working with law enforcement and customs agencies to prevent the sale and manufacture of counterfeit 3M respirators," the company said.