Canadian National Railroad officials are considering selling an unused railroad tunnel under St. Clair River in Port Huron that could become a new international border crossing for trucks.

The tunnel was built in 1891 and shut down in 1995 when a new and larger tunnel was built adjacent to it to accommodate multi-level rail cars. The tunnel connects Port Huron with Sarnia.

"CN is in the preliminary stages of looking at marketing the old tunnel as a truck tunnel alternative to alleviate truck crossings at the Blue Water Bridge," CN spokesman Mark Hallman said. The old tunnel is less than 20 feet in diameter and might only accommodate one-way traffic.

This is one of several plans to increase truck routes over the Canada-U.S. border. The Detroit River Tunnel Partnership is considering plans to convert an unused rail tunnel tube connecting Windsor and Detroit into a two-lane truck tunnel. The owner of the Ambassador Bridge, Detroit International Bridge Co., is working on plans to build a second bridge next to the existing span.