Coast Guard Lt. Justin Westmiller told the Detroit Free Press the bridge resumed commercial and recreational traffic at 1 a.m. after authorities swept the bridge for explosives.
A bomb threat was called in around 7:20 p.m. Monday, prompting the closure of the bridge and severely backing up commuter traffic, Detroit Police Inspector Don Johnson Jr. said. The Detroit News reported the call was made by someone in Detroit.
"There is a bomb at the Ambassador Bridge scheduled to go off in 10 minutes," the caller said.
The scare is the second in a week along the border, with another bomb threat called in Thursday regarding the Detroit-Windsor Tunnel. The tunnel was closed for search for more than four hours.