DETROIT – The Detroit-Windsor Tunnel has reopened after a bomb threat phoned in to Canadian authorities led to the closing of the international crossing for several hours.

The underwater tunnel is one of North America’s busiest trade crossings

Cars began entering the tunnel at the U.S. end Thursday afternoon, and tunnel chief executive Neal Belitsky says traffic resumed from the Canadian end soon after.

Belitsky says nothing was found in searches by video, bomb-sniffing dog and bomb squad personnel.

The bomb threat was made some time after noon to the duty free shop on a plaza on the tunnel’s Canada side.