The NFL faced its first outbreak of the novel coronavirus on a team during the season when the Tennessee Titans shut down in-person activities Tuesday after receiving eight confirmed positive test results among players and other personnel.

The Minnesota Vikings, who played the Titans on Sunday in Minneapolis, also suspended in-person team activities, including practices and face-to-face meetings, at least temporarily.

The NFL initially was proceeding Tuesday as though this weekend’s games involving the Titans and Vikings will be played as scheduled, pending further testing results, but cancellations or postponements remained possible.

“This is not unexpected; as Dr. Sills and others have emphasized, there will be players and staff who will test positive during the season,” NFL Commissioner Roger Goodell wrote in a memo Tuesday to all teams. Allen Sills is the league’s chief medical officer.

The Titans had three new positive test results among players and five among other team personnel Tuesday morning, the NFL and the NFL Players Association said in a joint statement.

“Both clubs are working closely with the NFL and the NFLPA, including our infectious-disease experts, to evaluate close contacts, perform additional testing and monitor developments,” the league and players’ union said. “All decisions will be made with health and safety as our primary consideration. We will continue to share updates as more information becomes available.”

The Titans announced later Tuesday they had placed defensive lineman DaQuan Jones, long snapper Beau Brinkley and practice squad tight end Tommy Hudson on their covid-19 reserve list, which can be utilized for players who test positive or for those found through contact tracing to have been exposed.

According to Goodell’s memo, those who tested positive “will be isolated, carefully monitored, and given all necessary medical care.” Their family members will be offered testing, Goodell wrote. Through contact tracing, the NFL identified and isolated those found to have been in close contact to the Titans players and personnel who tested positive. Those in close contact will receive additional testing, according to Goodell’s memo, which said the NFL also had followed up with Sunday’s game officials and others who worked at the Titans-Vikings game.

“These results confirm the need to remain diligent in implementing all of our health and safety protocols to the fullest extent,” Goodell wrote in the memo, a copy of which was obtained by The Washington Post.

Two people familiar with the situation characterized the Titans’ results as confirmed positive results and indicated that false positives are not suspected.

Goodell wrote in his memo that there had been no positive test results or reports of symptoms among Vikings players or staff members. The Vikings said earlier in a statement that they would “work closely with the NFL and NFLPA to monitor the situation, perform additional testing and determine when the facility can reopen.”

The Titans are scheduled to play the Pittsburgh Steelers in Nashville on Sunday. The Vikings are scheduled to be on the road Sunday to face the Houston Texans. The NFL just completed Week 3 on Monday and has not had a game canceled or postponed while operating during the pandemic.

“It’s on,” a person close to the situation said midday Tuesday of Sunday’s Titans-Steelers game. According to that person, the NFL was evaluating on a day-to-day basis to determine when to reopen the facilities of the Titans and Vikings. Another person with knowledge of the league’s response expressed similar sentiments and denied reports that a decision already had been made to shut down the Titans until at least Saturday.

Steelers Coach Mike Tomlin’s video news conference was pushed back to Tuesday evening, at which point he said: “We don’t have a lot of definitive answers about long term what the prognosis looks like. We’ve been given a mandate to prepare as if the game is going to be played and played on time. And so that is our mentality.”

If the Titans are prevented from practicing this week, the league could face a decision about whether to have them play Sunday. The game could be moved to Monday to give the Titans some practice time. Another contingency being mentioned Tuesday is moving the Titans-Steelers game to Week 7 (currently the Titans’ bye) and moving the Steelers’ Week 7 game in Baltimore against the Ravens to Week 8 (currently the bye week for the Steelers and Ravens).

Titans outside linebackers coach Shane Bowen did not travel with the team to Minneapolis for Sunday’s game, a 31-30 victory for Tennessee, reportedly because of a positive test result received Saturday.

Under the NFL’s testing procedures, the positive test results for Titans players and personnel received Tuesday would have come from tests performed Monday. NFL players, coaches and certain team staffers are being tested daily during the season except for on game days. The test results usually are returned within 24 hours and the league has procedures in place for follow-up testing in cases with unconfirmed positive results, attempting to address any potential issues with false positives.

All players and coaches leaguewide who tested Saturday were cleared to participate in Sunday’s games, people familiar with the results said previously. Atlanta Falcons rookie cornerback A.J. Terrell was placed on his team’s covid-19 reserve list Saturday, reportedly for a positive test taken Friday. Terrell became the second NFL player to miss a game this season for a coronavirus-related issue. An unidentified player was withheld from his team’s Week 2 game after testing negative but displaying coronavirus symptoms, multiple people familiar with the situation said at the time.

The NFL has been operating with strict protocols in place, including testing, distancing measures, contact tracing and mask-wearing. They address teams’ workweeks at their own facilities, travel to road games and game-day procedures.

Sills has stressed repeatedly that testing is valuable but not perfect and it is the entirety of the health and safety measures, not testing alone, that will keep players and others safe and allow the league to proceed with the season. Some NFL teams have allowed some fans to attend games, but most games have been played in empty stadiums.

Sills has said any decisions about game cancellations or postponements would be made by the league in consultation with the NFLPA, health experts and state and local authorities. The league also formed a committee of outside advisers to assist Goodell when considering the competitive implications of any team shutdowns or game postponements or cancellations. That committee includes former players Champ Bailey, Troy Polamalu and Isaac Bruce; former general managers Bill Polian, Charley Casserly and Rick Smith; and former coaches Tom Coughlin and Marvin Lewis.