NEW YORK — The NFL revealed Sunday that several false positive COVID-19 tests were found a day earlier by one of its testing partners. Among teams reporting false positives, the Minnesota Vikings said they had 12, the New York Jets 10, the Chicago Bears nine and the Pittsburgh Steelers six.

The league has asked the New Jersey lab BioReference to investigate the results “while the clubs work to confirm or rule out the positive tests.” The NFL did not identify the teams or say how many tests altogether were positive.

The number of positive COVID-19 tests from a specific facility that might actually be false demonstrates the precarious position the NFL is in less than three weeks from the regular-season opener.

The Steelers said the players will be back at practice Monday.