The Transportation Safety Board is calling on Canadian and U.S. regulators to take pains to ensure that hazardous materials are accurately classified.

The TSB, which investigates major transportation incidents, issued a safety advisory letter Wednesday morning, informing Transport Canada and the United States Pipeline and Hazardous Materials Safety Administration that the crude on a runaway train that devastated Lac-Mégantic was more volatile than its classification indicated.

Canadian investigators say the oil was inconsistently described, raising questions about the regulation of crude shipments in North America.

Story continues below advertisement

TSB investigators wrote in a letter to the two agencies that the material safety data forms they examined "varied widely" and were sometimes contradictory with respect to the properties of the oil on the train.

Stressing that its investigation is ongoing, the TSB called on regulators in Canada and the U.S. to review their procedures to ensure products are adequately described.

"It's important that dangerous goods in transport be properly described," said Donald Ross, the TSB's lead investigator, noting that workers need reliable information to safely handle such goods.

However, even if the oil had been properly classified, current rules do not require it to be transported in a different type of tank car. But Mr. Ross said the incident "calls into question" the adequacy of the rail cars used to transport such material.

U.S. authorities have suggested the volatile oil should be shipped in smaller quantities in rail cars.

Mr. Ross said proper classification would not have changed the way fire departments responded to the fiery train derailment.

The oil came from suppliers from the Bakken Shale formation in North Dakota, TSB investigators said. It was moved by highway trucks to New Town, where it was loaded into rail cars.

Story continues below advertisement

TSB investigators visited New Town after the accident in Lac-Mégantic and examined material safety data sheets from 10 different suppliers in the area. While all of the suppliers labelled the oil as a dangerous good, but they were not consistent in indicating how volatile it was.

At least four of the suppliers indicated that their crude should be designated packing group 1 – indicating the highest volatility – and two indicated that it was necessary to determine the flash point of the crude to classify it accurately. Another four classified their crude as either packing group 2 or 3.

Despite those differences, all of the shippers moving crude from the suppliers to a loading facility in New Town classified it correctly, as packing group 2.

Finally, when the crude was loaded into a train, the shipper billed all of the tank cars as the less hazardous group 3.

TSB officials concluded the lighter, more volatile crude should have been classified as group 2 oil – meaning it was as flammable as gasoline.

Investigators said it would be up to the importer of the crude – Irving Oil, in the case of the train that crashed in Lac-Mégantic – to ensure the product being imported is classified correctly.

Story continues below advertisement

Transport Minister Lisa Raitt issued a statement Wednesday saying she had directed Transport Canada officials to review the TSB letter "as quickly as possible."

"If a company does not properly classify its goods, they can be prosecuted under the Transportation of Dangerous Goods Act," Ms. Raitt said in the e-mailed statement.

NDP MP Olivia Chow, who is her party's transport critic, said Wednesday that the TSB revelations should be a "wake-up call" for the federal government.

"We have to end years of federal neglect and mismanagement when it comes to the transportation of dangerous goods," she said in an e-mailed statement.

Ms. Chow called for heightened testing and documentation requirements for dangerous goods and more spot checks and safety inspections by federal regulators.

Earlier this summer, the Transportation Safety Board issued two other safety advisory letters related to the crash in Lac-Mégantic. The board called for more detailed rules on the number of brakes that must be set on parked freight trains and a halt to the practice of leaving trains hauling dangerous goods unattended on a main track.