Canada's main opposition party called Thursday for tougher rail-industry regulations after a weekend derailment and explosion in a small Quebec town left 50 people dead or missing.

The New Democratic Party (NDP) notably pressed Prime Minister Stephen Harper's Conservative government to set a deadline for phasing out the use of DOT-111 tank cars in the transport of hazardous materials.

It also urged the end of the current practice of having a single engineer aboard a train "when dangerous goods are being transported."

Part of a train made up of 72 tank cars loaded with crude oil derailed in the early hours of Saturday in Lac-Megantic, near the Quebec-Maine border, igniting a huge explosion that laid waste to the center of the lakeside town. 

Twenty-four people have been confirmed dead and 26 remain unaccounted for with little hope of being found alive, Quebec provincial police said Thursday, as accident investigators continued to comb through the rubble.

The first victim to be identified was a 93-year-old local woman, the coroner's office said.

Police said another 600 people out of some 2,000 initially evacuated during the disaster were allowed to return on Thursday as police trimmed their area of search, but some 200 remain at shelters.

The train was hauling crude oil from North Dakota via Montreal and the northern part of Maine to a refinery in the Canadian Maritime province of New Brunswick.

The head of the US-owned Montreal, Maine and Atlantic Railway has faulted the train's engineer for failing to properly set the hand brakes before it raced out of control down the tracks into Lac-Megantic.

Canada's Transportation Safety Board says the DOT-111 tank car is widely used by railways across North America to carry products as varied as corn oil and petroleum products.

But critics say their single-wall construction -- compared to double-walled propane tank cars -- make them vulnerable to puncture and spillage in the event of an accident.

Canadian Transport Minister Denis Lebel has said that 350,000 of the half-million rail tank cars on Canadian and US railways are DOT-111 models which can typically carry 100 tons of oil each.

The NDP also appealed to Harper's government to make public "all audits" of Montreal, Maine and Atlantic's rail operations and to revoke its operating license "if their safety measures are inadequate."

The disaster has raised questions about the surge in shipments of crude oil on North American railways, at a time when Ottawa is pushing Washington to approve a major pipeline project through the US heartland.

Separately, Quebec Premier Pauline Marois, visiting Lac-Megantic for the second time since the disaster, condemned as "deplorable" the conduct of both the railway and its Chicago-based chairman Edward Burkhardt.

"In my opinion, he should have been on the scene from the outset of this incident," she said, a day after Burkhardt paid his first visit to the town to see the damage first-hand.

Burkhardt, an investor in railways in North America, Central Europe and New Zealand, has said it was more effective for him to remain in Chicago initially to deal with lawyers and insurers.

Marois, leader of the separatist Parti Quebecois, said the railway -- whose press releases translated into poor French angered many citizens -- should have done a better job communicating with townspeople and officials.

Quebec has released $60 million to help Lac-Megantic rebuild.

"We will do everything possible for the response to be adequate, efficient and immediate," Marois said.

(TTO)