As of Monday morning, the rotating strikes by Canada Post workers were underway at post offices in four Canadian cities.

At midnight Monday, about 100 employees walked off the job at the processing facility in the city’s northwest. The workers will be on strike for 24 hours.

Early Monday, night shift workers were on the picket line, with more workers expected to join them at 8 a.m.

The job action began after negotiators failed to reach a new contract agreement before the strike deadline.

Key issues for the union are job security, forced overtime due to an increase in online shopping, a need for better health and safety measures and gender equality.

“The fact they did not even touch these major demands over the weekend when we gave them five day strike notice is pretty indicative of where they are,” Nancy Dodsworth, CUPW Edmonton Local president said. “I’m hoping that these rotating strikes will start putting pressure on the corporation to let them know that we are serious and we do need these issues resolved.”

Striking workers also told CTV News they’d like to see wage increases to match inflation.

In Edmonton, the processing facility has stopped operating, and mail carriers will not work. The union said mail will still be delivered outside of the four cities, but it could be delayed.

The strike is impacting Canada Post facilities in Edmonton, Victoria, Windsor and Halifax. If the strike continues, more locations will be added.

Canada Post says it is committed to coming to a negotiated settlement.

With files from Jonathan Glasgow