Detroit police said a 911 call came in around 7:20 p.m. EDT to authorities on the U.S. side of the Ambassador Bridge "pertaining to a bomb on the bridge," police spokeswoman Sgt. Eren Stephens said. She said the call prompted authorities in both cities to halt all truck and car traffic across the bridge.
There were no immediate reports of authorities finding a bomb. Stephens said Detroit police are working with state and federal law enforcement agencies.
The closing of the busy freight crossing led to major traffic backups on expressways and other major roads leading into downtown Detroit, Stephens said. Car and light truck traffic was being diverted to the Detroit Windsor Tunnel about 2 miles away - but large trucks cannot use the underwater commuter tunnel.
On Thursday, a similar threat was phoned in to Windsor authorities and lead to a four-hour closing of the tunnel. No explosives were found.
At the time, police said a man had called from a street pay phone and warned of a bomb on the Canadian side of the tunnel, a busy border crossing beneath the Detroit River that connects the two border cities.