The NFL worked Sunday to assess a series of positive COVID-19 results that have all been traced to the same laboratory in New Jersey, raising concerns about the efficacy of the testing program established to minimize the spread of the disease.
"Saturday's daily COVID testing returned several positive tests from each of the clubs serviced by the same laboratory in New Jersey," the NFL said in a statement Sunday morning. "We are working with our testing partner, BioReference, to investigate these results, while the clubs work to confirm or rule out the positive tests."
All told, the NFL is investigating 77 test results from a total of 11 teams, a source told ESPN. The league is rerunning each test with the original sample and hasn't found any true positive cases. All 77 individuals also took point of care tests, all of which returned negative. NFL chief medical officer Allen Sills was slated to have a call Sunday night with team medical officials to share information and answer questions.
The Chicago Bears announced that they received nine positive results from their Saturday test regimen. All nine were determined to be false positive results, meaning none was an actual indication of infection. The Bears moved their morning practice to Sunday afternoon "out of an abundance of caution" while they sorted through the test results.
The Cleveland Browns said they received results that indicated multiple "presumptive positive" tests from players, coaches and support staff. However, upon retesting, the team found those to be false positives, "which is consistent with the irregularities across the league from multiple teams." After earlier canceling practice and closing their facility, the Browns said they reopened the building to "resume football activities" Sunday.
The Buffalo Bills pushed the start of their practice back by one hour, with general manager Brandon Beane confirming that some players were to miss Sunday's practice. Sources told ESPN's Adam Schefter that quarterback Josh Allen was among the NFL players to miss after receiving a false positive test, and he is expected to return Monday.
"We're just trying to be very cautious," Beane said. "We've been open with our team. The league jumped on this early to let us know that it wasn't just our team. It's a lot of teams."
The New York Jets had 10 tests come back as false positives, coach Adam Gase said. The team canceled a walk-through practice Saturday night but returned to the practice field Sunday after the retests came back negative.
The Pittsburgh Steelers released a statement Sunday saying that six players missed practice Saturday because of COVID-19 protocol, but all six were slated to return to meetings Sunday and practice Monday. A source told ESPN's Adam Schefter that all six were false positives.
Minnesota Vikings coach Mike Zimmer said eight players, a coach and three staff members had presumptive positive tests from the New Jersey lab and did not practice Sunday.
"Honestly for us, it's probably good that it happened now 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," Zimmer said.
Green Bay coach Matt LaFleur said the false positive COVID-19 tests that affected several teams caught a couple of Packers players, but the team was able to get it straightened out before practice, and "everybody that was supposed to practice [was] back out there."
The New England Patriots were also affected, a source told ESPN, but it wasn't viewed as something disruptive enough for them to cancel their scheduled practice Sunday. Veteran running back James White was one of five players who practiced Friday but weren't present Sunday; it was unknown whether all of those absences were because of false positive tests.
The Detroit Lions had one player with a false positive who is expected back at the facility Tuesday, a source told ESPN.
No players or coaches for the New York Giants tested positive, but the team was awaiting test results on some support staff members to see whether they were false positives, a league source told ESPN.
The NFL has been retesting the tests that came back positive from the New Jersey lab, and so far it is finding evidence that leads the league to believe that the issue involves testing irregularities, not a surge of positive tests.
"It's kind of crazy, you know, just thinking, what if that happens before a game or something?" Jets linebacker Avery Williamson said Sunday. "It's crazy. You just don't know what's going on. There's nothing you can really do. If somebody has it and you don't know it, and you're practicing against them and stuff ... I just hope we can stay as clean as possible."
In its statement, the NFL said that the affected clubs "are taking immediate precautionary measures as outlined in the NFL-NFLPA's health and safety protocols to include contact tracing, isolation of individuals and temporarily adjusting the schedule, where appropriate."
Any player who tests positive for COVID-19 -- even if it is found upon retest to be a false positive -- must have two negative tests before he will be allowed to return to practice.
According to league sources, NFL officials hope this experience can help inform game-day protocol to ensure that on game weekends, they can isolate those who are sick and leave enough time for confirmatory tests so that they can work around issues such as this and so that games aren't affected by testing irregularities.
"My question immediately would be: If you realize it's a lab issue, would a point-of-care test on the game site -- if it was negative -- would that allow the player to play?" Beane said Sunday. "And I don't have that answer, but that's the question that we'll have to see how the league would respond to that.
"... Probably better that this happened now than three weeks from now. But it seems like every few weeks, every week, something's going on, and so who knows what the next curveball will be?"
The Las Vegas Raiders, who were off Saturday, switched from a scheduled full, padded practice with media viewing to more of a physical "maintenance" day for players, without media, on Sunday. A team spokesman said the switch was not related to the NFL's COVID-19 testing issues.
The NFL said other BioReference laboratories used for NFL testing have not had similar results to that of the New Jersey lab. NFL testing is conducted exclusively by BioReference, but the tests are serviced by labs around the country to ensure results in 24 hours or less.
The league has so far avoided team outbreaks during training camp. As of Sunday, only three of the nearly 3,000 players who have spent time in training camp were on the reserve/COVID-19 list.
ESPN's Dan Graziano contributed to this report.