Commercial truck traffic at Canada's largest international land crossings is being delayed for hours as customs and immigration officers step up inspections following terrorist attacks on New York and Washington, D.C.

According to website of the Canadian trucking publication Today's Trucking, southbound traffic at North America's busiest commercial border crossing, the Ambassador Bridge in Windsor, Ont., was so extreme that the Canada Customs and Revenue Agency would not provide estimated waiting times.
Shortly after midnight today, trucks were backed up 25 km on both lanes of Hwy. 401. The wait for clearance by U.S. customs and immigration officials was eight to 12 hours.
The Ontario Provincial Police warned truck operators not to use crossings in the Niagara region. Bridges to the United States are open, but flows are severely restricted. At Fort Erie, Ont., OPP was diverting trucks to a nearby racetrack and was releasing 20 at a time.
However, northbound traffic into Canada was flowing with little delay. The CCRA has been posting estimated crossing times at its web site. The information is updated every four hours.
Security has also been tightened at the Mexican border, At least 300 vehicles were backed up in each lane in Tijuana, Mexico, on Wednesday, double the usual number, according to the Associated Press.