According to Customs and Border Patrol agents, the knock-offs were intended for hospital workers on the east coast.
The masks had 3M labels, but the company worked with agents to determine they were fake.
Agents believe the retail value of the masks was more than $600,000.
Because the masks are counterfeits, there's a good chance they don't work.
Authorities say half of all counterfeit goods that enter the U.S. originate from China.
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