More than 1,800 Canada Post workers have walked off the job in Hamilton and La Mauricie, Que., as the union's overtime ban becomes effective across the country.
The Canadian Union of Postal Workers says the walkout in La Mauricie began Wednesday at 11:30 p.m. and in Hamilton just after midnight on Thursday.
Those workers joined union locals in 12 other communities taking part in the rotating strikes.
The Ontario communities of Arnprior-Renfrew and Ottawa are still on strike, as well as the British Columbia cities of Campbell River, Courtenay, Nanaimo and Port Alberni.
In Quebec, six Canada Post locals are also off the job, including St-Jerome, Valleyfield and Sorel.
On Wednesday, CUPW said the overtime ban means postal workers can refuse to work beyond their normal eight-hour days.