SARNIA, Ont. - A tunnel linking Sarnia, Ont., and Port Huron, Mich., has reopened after a freight train derailment last month.

CN says crews finished laying new track in the international tunnel and the first train successfully went through on Tuesday.

A CN freight train derailed on June 28, sending about 40 cars off the tracks, but no fires or injuries were reported.

The rail company says the tunnel only received minor damage and there was no impact to its "structural integrity."

One car containing sulphuric acid leaked, but the company says the substance was contained to the site and posed no danger to the public or the St-Clair River.

The Transportation Safety Board said the investigation into the derailment is ongoing.