Some of the tanker cars involved in the accident are the Dot-111 model, that have raised safety concerns for as many as two decades.

In a report, the U.S. National Transportation Safety Board said the tanker car housings on the Dot-111 are not effective in preventing damage in case of derailment.

It has found in numerous investigations that stronger protective shells are needed in order to prevent tragedies of this magnitude.

Despite these findings, the model continues to be used to carry crude oil about 70 per cent of the time, because they remain authorized for use by the Canadian and American governments.

The only stipulation is that as of 2011, Ottawa made it mandatory that any rail company updating its fleet must choose tanker cars with thicker shells.

In the weekend derailment in Lac-Megantic, the Montreal, Maine and Atlantic company said it was leasing the cars in question, but said as far as it knows everything was up to code, despite warnings from the American National Transportation Safety Board.

“They haven't been successful in imposing any kind of regulation on those cars, or else they would not be in service,” said company president Edward Burkhardt. “The cars as far as we are concerned are in compliance with the Association of American Railroads (AAR) and federal railroad administration, and Transport Canada regulations.”

Berkhardt said he will be in Lac Megantic to oversee his company's invesitgation by Wednesday or Thursday of this week.

Meanwhile, many are criticizing the company -- first of all for using this particular tanker car model -- but also because such a dangerous substance was being transported on a Class 2 track network. Less train traffic travels on Class 2 networks, meaning there is less government funding to maintain the tracks.

Denis Allard of the World Railway Heritage Fund said it’s appalling.

“It is completely absurd that Montreal, Maine & Atlantic attached 73 wagons behind a train on a network that isn't in good condition,” he said.

Rail companies, as well as the Canadian and U.S. governments will be receiving a series of recommendations concerning the type of tanker cars used for the transportation of dangerous materials, as well as the maintenance of the railway network.

The investigation into the explosion continues.