An unconfirmed report indicates the failure of an air hose led to the derailment of nearly 50 rail cars in the St. Clair Tunnel June 28.
Sources have told Blackburn News the failure triggered the brakes on the first part of the CN train to make an emergency stop while the rear section continued rolling. A communication blackout while trains travel through the tunnel between Sarnia and Port Huron, Michigan is said to have been a contributing factor. There was a lack of radio communication between the lead and mid-section locomotives and the communication beacon at the rear of the train.
The Transportation Safety Board of Canada (TSB) is investigating the derailment that shut down the tunnel for 11 days.
When asked about the suspected cause, the TSB said the investigation is ongoing and it has no new information to share at this time.
"Investigators will, of course, be looking at a broad variety of factors as they continue their work, but it is too soon for any conclusions," spokesperson Julie Leroux said in an email to BlackburnNewsSarnia.com. "Investigations are complex, and we, therefore, take the time necessary to conduct a thorough investigation to advance transportation safety. Be assured that, if we uncover serious safety deficiencies during the course of our investigation, we will not wait until the final report to make them known. We will inform industry and the regulator as quickly as possible."
Leroux said the incident has been classified as a Class 3 which requires a detailed investigation with a target timeline of 450 days.
Following the derailment, CN employees and contractors worked around the clock to get the tunnel back in service, and a train successfully cleared the tunnel for the first time since the incident on Tuesday, July 9.
CN Rail said crews laid new track for the whole span of the tunnel beneath the St. Clair River.
Spilled sulphuric acid was removed from the site or neutralized and the tunnel suffered only minor cosmetic damage with no impact to its structural integrity.
The rail company also said the spill was completely contained to the site of the derailment and caused no harm to the environment or to public safety.