The Windsor-Detroit tunnel reopened at 5 p.m. after a closure early Thursday afternoon while police on both sides of the border were investigating a bomb threat.
The warning of a non-specific bomb threat came from an anonymous caller on the Canadian side, possibly from a telephone booth in Windsor, said Sergeant Matthew D'Asti of the Windsor Police Service.
The Detroit police canine unit entered the tunnel from the U.S. side, sweeping the entire tunnel as they made their way to the Windsor side, he said, adding that they were satisfied the tunnel was clear.
Traffic in both directions of the tunnel was closed at 12:53 p.m., and the Canada Border Services Agency was recommending travellers use the Ambassador Bridge.
"This was perceived as a threat at a major international border crossing, so an investigation was mandatory," Sgt. D'Asti said, adding he was unsure how many anonymous threats the police have received at this border.