CHICAGO (WLS) -- A main route from the Midwestern United States to Canada was mysteriously shut down Monday after authorities reported possible explosives near the Ambassador Bridge between Detroit and Windsor, Ontario.
Traffic was halted in the morning on one of the busiest days for truck traffic between the U.S. and Canada.
Authorities said there were suspected explosives found inside a vehicle on the Canadian side of the Ambassador Bridge. The area was evacuated and most of the day bridge traffic was shut down in one direction or the other.
Freight and cargo trucks to and from Chicago, the Plains and the entire Midwest depend on the Ambassador Bridge that connects Detroit to Windsor, Ontario.
It's the busiest international land border crossing in North America, but it wasn't earlier in the day, when a secondary inspection point exposed possible explosives in a vehicle.
The driver was detained by Canadian border authorities although the person's name, any charges and the circumstances of the incident haven't been released.
For hours, the span over the Detroit River was closed off to more than 40,000 truckers, commuters and tourists who cross each day.
The Windsor police bomb squad deployed a robot to investigate the vehicle and suspicious components that had caused the shutdown.
Investigators said they are not aware of any direct threat made to blow up the bridge, although they haven't said exactly what the possible cause was for the shutdown.
Vehicles that weren't already caught in the gridlock were routed to the Detroit-Windsor Tunnel.
Late in the afternoon, the Canadian border services tweeted the Port of Entry was reopening.
All lanes of the Ambassador Bridge are now back in service although authorities still urging motorists, especially truckers, to consider alternative routes to avoid delays caused by a daylong backup of traffic.
After the September 11, 2001 terror attacks, entry to the U.S. at the Detroit/Canada border was significantly tightened. It remains so to this day.
Monday's shutdown isn't the first time the Ambassador Bridge has been closed because of a bomb threat. In the decade after 9/11, there was a string of threats that closed off bridge traffic, even as motorists and cargo trucks took alternate routes to avoid the customs checkpoint that had become a chokepoint.
Ambassador Bridge between US, Canada shut down for hours after suspected explosives found
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