OTTAWA — Canada’s transportation safety authority said the crude carried on a train that crashed in Quebec, killing 47 people, should have been labeled as being more dangerous.

An unattended Montreal Maine & Atlantic Railway Ltd. train with 72 tankers of crude crashed in the Quebec town of Lac-Megantic in July, causing the worst Canadian rail disaster in more than a century. The Transportation Safety Board said in a statement from Ottawa Wednesday that the oil was labeled as a “lower hazard, less volatile flammable liquid.”

“Test results indicate that the level of hazard posed by the petroleum crude oil transported in the tank cars on the accident train was not accurately documented,” the agency said.

The TSB said it sent letters to U.S. and Canadian regulators asking them to review processes for identifying and labeling dangerous goods. The agency has already asked Canadian regulators to impose stricter rules on securing unattended trains and staffing of trains carrying dangerous goods.

The receiver of the shipment, Irving Oil Corp., was responsible for labeling the content of the train cars, Ed Belkaloul, the agency’s manager for operations in Quebec, told reporters Wednesday at a news conference near Ottawa. The train was carrying crude to Irving Oil’s refinery in Saint John, New Brunswick from North Dakota’s Bakken region.

Carolyn Van der Veen, a spokeswoman with Irving Oil, didn’t immediately respond to a telephone call and e-mail seeking comment.

Last month, U.S. railroad regulators announced a Bakken inspection “blitz” aimed at ensuring crude oil being hauled from the region in tank cars is labeled accurately. The Federal Railroad Administration and Pipeline and Hazardous Materials Safety Administration began planning for increased inspections of tank cars carrying Bakken crude in March, four months before the July 6 Lac-Megantic crash, the heads of the two agencies told reporters Aug. 29. U.S. regulators had noticed “inconsistencies with crude oil classification,” PHMSA has said.

The Bakken inspection blitz is still going on, Kevin Thompson, a spokesman for the U.S. Federal Railroad Administration, said in an e-mail.

There are three categories of dangerous goods within class 3, which involves flammable liquids. The TSB said samples from cars involved in the Quebec crash had characteristics of a category 2 shipment, which is more explosive than the category 3 that appeared on the labels.

“We share the TSB’s concern,” said National Transportation Safety Board Chairman Deborah Hersman in a statement from Washington. “Clearly understanding the hazardous characteristics of what is being transported is one of the keys to safe transportation.”

The crash “also brings into question the adequacy of Class 111 tanks cars for use in transporting large quantities of low flash flammable liquids,” the Canadian regulator said in the statement.

Jeannie Layson, a spokeswoman for PHMSA, had no immediate comment.