The tests were reportedly contaminated with COVID-19 "during test preparation" at a New Jersey laboratory
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The National Football League has cleared its players and staff after a series of false positive coronavirus tests over the weekend.

On Monday, BioReference, a clinical laboratory company that the NFL hired to conduct all of its COVID-19 testing, released a statement revealing that the positive coronavirus tests from Aug. 22 were "caused by an isolated contamination during test preparation."

"On August 22, BioReference Laboratories reported an elevated number of positive COVID-19 PCR test results for NFL players and personnel at multiple clubs," the statement, released online, said. "The NFL immediately took necessary actions to ensure the safety of the players and personnel."

"Our investigation indicated that these were most likely false positive results, caused by an isolated contamination during test preparation in the New Jersey laboratory," it continued. "Reagents, analyzers and staff were all ruled out as possible causes and subsequent testing has indicated that the issue has been resolved. All individuals impacted have been confirmed negative and informed."

Sources told ESPN that 11 teams were affected by the results, with a total of 77 individuals coming back with positive coronavirus tests.

The NFL responded quickly, retesting the original 77 samples, which had all been processed at the same BioReference lab in New Jersey. All of the retests came back negative.

The league also conducted a second round of rapid point-of-care tests on Sunday, and all 77 of those also came back negative.

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Teams most affected by the false positive scare included the Minnesota Vikings, who had 12 tests come back positive, the New York Jets with 10, and the Chicago Bears with nine.

Vikings coach Mike Zimmer told ESPN he's happy this happened now, giving teams a trial run on how to deal with a similar situation in-season.

"Honestly for us, it's probably good that it happened now," Zimmer said. "Because we were able to adjust and adapt and figure out the kinds of things that would happen if it did happen during the season and what we would do from there."

After getting back the false positives, teams worked to adjust their Sunday practice schedules to contain the spread and protect healthy players and staff.

Buffalo Bills general manager Brandon Beane agreed with Zimmer, calling the experience a "good fire drill" for coaches.

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