The Transportation Safety Board of Canada revealed on Wednesday the cause for a CN train derailment near Clair in 2014 that caused Highway 5 to be closed and the community evacuated.

An investigation found that the a broken rail due to an undetected defect led to the derailment.

A total of 26 railcars, including six with dangerous goods went off the rail on October 7, 2014. Two of the cars were loaded with petroleum distillates, which caused a fire.

Clair, which housed 50 residents, was evacuated within an eight kilometre radius, and the section of Highway 5 in the area was blocked off.

While there were no injuries, a flash fire put responders in danger after vapors inside one of the tank cars ignited, sending a massive fireball towards two of the responders.