The NHL and National Hockey League Players' Association have returned to tighter COVID-19 safety measures.

The league confirmed Saturday morning that it was adopting, effective immediately, new rules amid the emergence of the Omicron variant and the explosion of positive test results, particularly in the past few days.

Measures include restrictions on indoor dining while on the road, wearing masks while in club facilities and during travel, including when on buses, planes and at the hotel, and daily testing, expect on days off.

Additional pre-game testing may be implemented on a case-by-case basis, when an outbreak occurs within a team.

Players are urged to wear N95, KN95 or surgical masks rather than cloth masks. Club-organized holiday parties are not permitted, and all members of a team's travelling group are prohibited from signing autographs or engaging with fans.

The announcement comes a day after the league shut down the Calgary Flames, Colorado Avalanche and Florida Panthers because of COVID-19 concerns. The Flames have 32 people in the NHL-'s COVID-19 protocol, 19 players and 13 club employees.

These enhanced measures, meant both to prevent the contraction or transmission of COVID-19 and early detection of positive cases, will remain in effect through the holiday season, and will be re-evaluated by Jan. 7 by the NHL and NHLPA.

“Given the increased number of positive cases in our league within the last two weeks, and changing societal realities with the new omicron COVID-19 variant, the NHLPA and NHL have collectively agreed that all dlubs shall be required to follow enhanced preventive and detection measures,” the league said.

Moments after the announcement, Detroit placed three players, coach Jeff Blashill and assistant coach Alex Tanguay in protocol ahead of Saturday night's home game against New Jersey.

Grand Rapids Griffins head coach Ben Simon and assistant coach Todd Krygier have been called up to work the bench tonight alongside Red Wings assistant Doug Houda for Detroit's home game against the New Jersey Devils.

The Red Wings have the only player in the league, Tyler Bertuzzi, who is not vaccinated.

While postponed games may be rescheduled, all eyes on are the calendar: The NHL plans to allow its players to participate in the Winter Olympics in China in February - unless COVID-19 disruptions prove to be too much.

The NHL has until Jan. 10 to opt-out of the Winter Games without financial penalty, but retains the right to cancel its plans up until players are scheduled to travel to Beijing.

With files from The Associated Press

This report by The Canadian Press was first published Dec. 18, 2021.