commuter tunnel connecting Detroit to Windsor, Ontario, was closed for nearly four hours Thursday after a bomb threat was phoned in on the Canadian side. No explosives were found.The Detroit Windsor Tunnel, a busy border crossing beneath the Detroit River, was shut down after a duty free shop employee on the tunnel’s Canadian plaza reported receiving a call about a bomb threat shortly after 12:30 p.m.The tunnel was eventually closed and traffic on both sides of the river was directed to the nearby Ambassador Bridge, which spans the river, tunnel executive vice president Carolyn Brown said.Homeland Security, U.S. Customs and Border Protection, Detroit police and other agencies flooded the plaza and entrance on the tunnel’s American side.Bomb-sniffing dogs from a number of federal and local agencies were called in, said Donald E. Johnson, head of Homeland Security for Detroit police.“What we actually did was the actual sweep of the entire tunnel for any type of explosives,” Johnson said.Cars and buses were allowed back through the tunnel shortly after 4:30 p.m. Traffic
from Canada resumed a few minutes later.The 82-year-old tunnel stretches about a mile across the Detroit River, which is one of North America’s busiest trade crossings.Cars and buses make up most of the traffic. About 4.5 million cars crossed in 2011.The bomb threat also resulted in heightened security along the Ambassador Bridge, just west of downtown Detroit.“As security concerns were made, customs became a little more thorough at the bridge,” said Ambassador Bridge spokesman Mickey Blashfield.Brown said the security steps appeared to run smoothly.After the call came in, officials at the tunnel followed protocol that’s established between the tunnel operators and local emergency services officials in consultation with U.S. Customs and Border Protection, tunnel officials said.“We practice this,” Brown said. “Once a year we do a full-blown exercise. We shut it down on a Sunday morning and we have all the first responders in. We simulate an accident or an incident.”Since 1998, there have been nearly $50 million in facility, safety and security upgrades at the tunnel, said Neal Belitsky, tunnel chief executive.