A vendor informed the health network, with seven hospitals from Berks to Philadelphia, that the masks, which had been thought to be made by 3M were fake.
The vendor said 3M notified them on Feb. 3.
"We had used an alternative vendor to acquire these masks because our primary supplier was not able to meet our demand," Tower Health said in a statement. "Our alternative vendor was supplied what it thought were 3M N95 masks, but which were counterfeit."
Tower Health said it distributed about 12 percent of the masks before its supply chain team responded and recalled the fake ones.
The federal government sent out a warning earlier this week telling people and companies to be on the on lookout for compromised masks.
These masks are giving first responders "a false sense of security," said Steve Francis, assistant director for global trade investigations with the Homeland Security Department's principal investigative arm. He added, "We've seen a lot of fraud and other illegal activity."
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3M, based in Maplewood, Minnesota, is among the largest global producers of the N95 mask, which has been approved by the U.S. National Institute for Occupational Safety and Health and is considered the gold standard in protection against the coronavirus. The company delivered some 2 billion N95 masks in 2020 as the pandemic soared, but in earlier months of the pandemic, when masks were in short supply, fraudsters starting popped up.
"They're not coming from authorized distributors," said Kevin Rhodes, 3M's vice president and deputy general counsel. "They're coming from companies really just coming into existence."
Rhodes encouraged medical facilities and even workers to look on the company's website for tips on how to spot fakes, namely through packaging or faulty trademarks.
"These products are not tested to see if they make the N95 standards," he said "They're not interested in testing them. They're interested in making as many as they can as cheaply as possible."
During the pandemic, Homeland Security Investigations has used its 7,000 agents in tandem with border officials, the Food and Drug Administration and the FBI to investigate scams, seize phony products and arrest hundreds of people to help stop fraud. The effort is based at the National Intellectual Property Rights Coordination Center, a government watchdog aimed at enforcing international trade laws and combating intellectual property theft.
There have been already more than 1,250 raids by law enforcement that resulted in the seizure of 10 million counterfeit 3M masks alone. The company has filed more than a dozen lawsuits over reports of fraud, counterfeiting and price gouging.
N95 masks block 95% of large and small particles utilizing a unique electrostatic filter.
The filter works by trapping neutral particles like bacteria and viruses before they pass through the mask, protecting the wearer and those around them. It's similar to how socks might get stuck to a blanket in the dryer. The N95 mask also fits securely to the face, eliminating most of the leakage that may occur with a loose-fitting cloth or paper mask.
ABC News and The CNN Wire contributed to this report.