(CNN) -- A bomb threat shut a major tunnel between Windsor, Ontario, and Detroit on Thursday, triggering traffic backups as drivers on both sides of the border were rerouted.
Employees at the Detroit-Windsor Tunnel received an anonymous phone call around 12:30 p.m. from someone saying there was a bomb in the tunnel, Sgt. Matthew D'Asti with Windsor police told HLN.
Authorities were treating it "as a non-specific anonymous bomb threat," he said.
The tunnel was evacuated.
When D'Asti spoke with HLN shortly after 2 p.m. ET, no bomb had been found.
Authorities were working together on both sides of the border to investigate, he said.
The tunnel is one of two international crossings for the cities of Windsor and Detroit.
It was unclear how long the tunnel would remain closed, D'Asti said. The "entire length of the tunnel will have to be searched," he said.
Authorities were working to trace the bomb threat call, he said.
By the CNN Wire Staff
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