The B.C. Ambulance Service warned Saturday that low-priorty calls would be delayed because of a staffing shortage. (CBC)

The B.C. Ambulance Service is urging residents throughout B.C. to call 911 only in life-threatening situations after a number of paramedics booked off their shifts with little notice Saturday.

In a written release, the B.C. Ambulance Service said more than 50 paramedics booked off their scheduled shifts just prior to the shift start time.

On Saturday, 10 ambulances were out of service in Metro Vancouver and 10 more in the Fraser Valley.

Three were out of service in the Sea to Sky Corridor and no ambulances were staffed in Boston Bar, Hope, Agassiz or Pemberton.

Only one ambulance was available in Mission and Whistler.

The B.C. Ambulance Service says the move is likely a protest after members of the B.C. legislature pushed through a bill ordering B.C.'s 3,500 ambulance paramedics back to work last Saturday, ending a strike that started in April.

Lee Doney, the CEO of the B.C. Ambulance Service, said this degree of absenteeism has never happened before.

"I understand that paramedics are frustrated. Tempers are high because of the back-to-work legislation, but this is no way to protest. Putting people's lives at risk is no way to protest," he said.

However, John Strohmeier, the president of CUPE Local 873, said the union had nothing to do with the cancelled shifts.

"There is a pandemic going on right now. I suspect that any paramedics that may be symptomatic are probably following the advice of the province's chief medical officer and staying home," he said.

"So I don't think there's any concerted effort by paramedics here. It's just a question of there not being enough staff to begin with."

The B.C. Ambulance Service said low-priority calls would likely be delayed but all emergency calls would be handled on a priority basis.

People with minor injuries or illness were advised to visit their doctor's office or walk-in clinic.

With files from The Canadian Press