Around 23:30, the train left Dorion, Quebec, using the north main track. While the train was travelling at 50 mph, it passed the 221 signal (Smith Falls Subdivision milepost 22.1), which was showing a clear indication. The crew noticed that the track ahead was obstructed by debris. The engineer reduced the throttle and initiated an emergency brake application. The train was unable to stop before hitting the clay debris and derailing. Looking westward - Date unknown Transportation Safety Board.

5 December 2011

The Transportation Safety Board of Canada Releases Investigation Report into the September 2010 Freight Train Derailment Near St-Lazare Quebec

Gatineau Quebec - The Transportation Safety Board of Canada (TSB) today released its final investigation report (R10D0077) into the 23 Sep 2010 derailment of a Canadian Pacific Railway freight train near St-Lazare, Quebec.
 
On 23 Sep 2010, a freight train consisting of 2 locomotives and 54 container cars was proceeding westward from Dorion, Quebec.
 
After passing a signal showing a clear indication, the crew noticed debris on the track ahead, attempted to stop the train, but could not stop it in time.
 
The train struck the debris and derailed 2 locomotives and 11 cars near St-Lazare.
 
The accident caused minor injuries to both crew members and a small spill of dangerous goods.