A bomb threat shut down a major commuter tunnel between Detroit and Windsor, Canada on Thursday, causing traffic jams on both sides of the border, according to CNN.
The tunnel reopened after several hours and cars entered the tunnel at 4:30 p.m., according to the Associated Press.
Neal Belitsky, the president and CEO of Detroit-Windsor Tunnel, said, "Nothing was found," according to the Detroit Free Press.
Workers at the Detroit-Windsor Tunnel received an anonymous phone call around 12:30 p.m., saying that there was a bomb in the tunnel, according to Sgt. Matthew D'Asti of the Windsor police, CNN reported.
Around 4.5 million cars used the tunnel in 2011, and it is one of two international border crossings in Detroit, according to the AP.
While the tunnel was closed, commuters were told to use the other international border crossing, the Ambassador Bridge, according to Detroit Police officer Cassandra Lewis. Lewis told Reuters that a Detroit police bomb squad was en route to the tunnel.
According to the Detroit Free Press, a K9 unit was inspecting the tunnel shortly before 2:30 p.m. Detroit fire spokesman Chief Kwaku Atara said fire and police officials were on the scene but there appeared to be no need for the hazmat team. A fire engine and an EMS rig were on stand by, he said.