Prime Minister Justin Trudeau said Wednesday protests near CN Rail tracks close to the Tyendinaga Mohawk Territory are a worry and the protesters could cause serious harm if they don't stop.

Protesters set tires on fire and tossed them onto the track Wednesday near Belleville, Ont., as CN Rail trains rolled by. Freight trains often carry flammable chemicals and petrochemical products.

Speaking to reporters outside the Commons today, Trudeau said the government is looking for a resolution to the Indigenous-led protests — which continued even after the Ontario Provincial Police made a series of arrests in the area on Monday to permit trains to move.

"We're continuing to work as we have over the past week. It is extremely concerning to see people endangering their own lives and the lives of others by trying to interfere ... with the trains. But again, we are continuing to work very hard to resolve this," Trudeau said.

A fire burns on CN Rail tracks in Tyendinaga, near Belleville, Ont., on Wednesday. (CBC)

Transport Minister Marc Garneau said the tire fires were "extremely reckless. I hope we're not going to see this kind of thing ever again."

Public Safety Minister Bill Blair also urged the protesters to stop this sort of activity.

"I think it's terribly unsafe and inappropriate," Blair told reporters.

"I would, again, continue to urge people to take the barricades down, to obey the law and encourage the dialogue that we know is so important to continue."

Freight traffic has started moving again through the area near the territory of the Mohawks of Tyendinaga, where protesters acting in solidarity with Wet'suwet'en hereditary chiefs opposed to the Coastal GasLink project set up camps.

Seven trains rolled through Belleville Wednesday, according to Garneau's office.

Garneau's office also said that by Wednesday evening, demonstrators had cleared out of protest sites in Caledonia, Ont. and B.C., making Kahnawake, Que. the last remaining blockade causing disruptions.

Crown-Indigenous Relations Minister Carolyn Bennett and Indigenous Services Minister Marc Miller have made another request to meet with the Wet'suwet'en hereditary chiefs opposed to the pipeline development. So far, those requests have gone unanswered.

The ministers said they had hoped to hear back from the chiefs by Wednesday afternoon about a meeting but, as of 5:30 p.m. ET, the timing of a possible meeting had not been settled.

Garneau's office said CN is getting its operations back online, but it could take weeks to return to normal service and clear up the backlog.