The blockade is at Marysville, Ont., between Belleville and Kingston.
Via Rail's media relations manager Jacques C. Gagnon said Marysville is a popular site for railroad blockades.
"We had hints since late last night that there would be a blockade," Gagnon said.
Train service between Montreal and Ottawa is still running.
However, trains travelling in the Montreal-Toronto corridor have been replaced by chartered buses.