LAPD Chief Michel Moore has told his officers the city is entering a new phase in its response to the coronavirus pandemic and could begin to move officers to 12-hour shifts with fewer days off as soon as Monday.

That mobilization strategy was last used by the department more than 20-years ago and can be implemented in times of emergency, Moore said.

Last week, he directed about half of the LAPD’s detectives to begin working in uniform, so there would be enough officers to handle increased crowd and traffic control calls and “high visibility patrols.”

Multiple law enforcement sources told NBC News that senior LAPD officials have grave concerns about coronavirus infections spreading among officers, who would then have to be isolated and removed from work while the officers are tested or treated. That officer shortage could lead to longer shifts for officers still working.