An improvised explosive device and four handguns were found in a car, after Canadian officials at a border crossing became suspicious of the driver, authorities said Wednesday. The bomb and firearms were found in the car, just after it had passed through the Peace Arch border crossing at about 9:30 p.m. Tuesday, Royal Canadian Mounted Police said in a statement. The explosive device was found in the engine compartment, officials said. Interstate 5 in the United States and Highway 99 in Canada were closed at the crossing - the busiest between the two countries west of Detroit, Michigan. Officials discovered the weapons and bomb after becoming suspicious of car, occupied only by the driver, a man acting erratically, said Paula Shore, spokeswoman for the Canada Border Services Agency. The Mounties' explosives squad was summoned, she said.