Updated

Canadian transportation safety officials have told U.S. officials that the oil carried by the train that derailed in Quebec in July was misclassified as a less dangerous type of crude.

The board's chief investigator, Donald Ross, said Wednesday the train's shipment of North Dakota crude oil was mislabeled as "Group 3" conventional crude, when it should have been given a more explosive "Group 2" classification.

The unattended train carrying oil from the Bakken region rolled away and derailed, with several of its oil tankers exploding in the middle of the Lac-Megantic, near the Maine border. The explosions and fire killed 47 people.

Safety regulations for the transport of crude oil differ depending upon the type of oil and its flashpoint — the lowest temperature at which it will ignite.