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Companies should be on the lookout for workers submitting fake positive COVID-19 test results as a get-out-of-work-free card, the FBI warned.

In a report issued Monday to various companies nationwide and obtained by CNN, the FBI’s Office of Private Sector warned employers to keep an eye out for fake doctor’s notes and falsified documentation from employees about their coronavirus status.

In one costly incident, according to the FBI report, an employee with an unidentified “critical manufacturing company” told their bosses they had tested positive for COVID-19 and submitted phony documentation purporting to be from a medical facility.

“In response, the company shut down the affected manufacturing facility to disinfect the location, ceasing production and halting delivery of necessary materials to the plant,” according to the report, obtained by CNN. “The company notified all employees at the facility, including four workers who had close contact with the reportedly infected employee and were required to self-quarantine.”

It wasn’t until supervisors closely examined the documentation that they realized it wasn’t on official letterhead — and called a number on the form to find that the location was not conducting coronavirus testing at the time.

But it was too late — the company incurred more than $175,000 in lost productivity over the alleged scam. And one co-worker who opted to self-quarantine in a rental property away from family — believing they had been exposed — suffered personal financial loss, according to the report.

The bureau urged employers to always contact medical providers listed on work excuse documents to confirm their veracity — and check for any inconsistencies in font and spacing, or signs of computer editing.

The FBI did not comment to CNN about any specific report, but said it “regularly shares this type of information that we assess as important, and we also respond to requests from our private sector partners for information on specific topics.”

One such scam happened last month, when Jeffery Travis Long of Spartanburg, South Carolina, used a forged doctor’s excuse claiming he had the virus, ultimately causing his company to shut down for five days, WSPA reported.

“Seems to me like the fellow just wanted a two-week paid vacation,” Sheriff Chuck Wright said at the time.

Also last month, in Hamilton, Canada, an 18-year-old employee submitted a fraudulent doctor’s note claiming she had tested positive for the deadly bug.

“The restaurant remained closed for several days while professional cleaning services worked to sanitize the store,” local police said. “There has been a significant impact on the restaurant, local customers and employees which instigated the need for police involvement.”