Canadian and U.S. fire crews have responded to a train derailment in the St. Clair Tunnel.
About 40 cars jumped the track on the U.S. side of the tunnel, which connects Sarnia with Port Huron, Michigan.
No injuries have been reported and there is no known public risk or off-site impact, Sarnia Fire Rescue Service said.
One tank car containing sulphuric acid was breached inside the tunnel. The contamination was contained and environmental monitoring is ongoing, Sarnia Police said.
Local officials responded about 5:30 a.m., and a reconnaissance team was sent into the tunnel to investigate, crews said at the scene.
Sarnia Fire’s hazardous materials unit was present at the site.
Canadian and U.S. officials are working alongside CN staff.