Police on both sides of the U.S.-Canada border gave the all-clear after a search of the tunnel Thursday.
Carolyn Brown, executive vice president of the tunnel's operating corporation, said a phone caller told police there was a bomb in the tunnel, prompting it to be closed while police investigated, CBC news reported.
The tunnel was evacuated in both directions, CBC News said.
Law enforcement officials turned away pleasure boats and freighters on the Detroit River while bomb squads searched the tunnel.
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