The firearms - a 9 mm handgun, two shotguns, and a rifle with a rifle stock - were found in an initial inspection of the car and the device, which turned out to be not explosive, was found in the engine compartment, according to a statement posed on the RCMP's Web site.

The device "had some wires protruding from it and was suspicious in nature," but the Mounties' explosives squad determined that it did not contain explosives, according to the statement signed by RCMP Cpl. Roger Morrow.

In a telephone interview with The Associated Press, RCMP Cpl. Steven Han described it as "a small device that looked like an improvised explosive device ... possibly a pipe bomb." He said he did not have the exact dimensions, and it was unclear how long it took investigators to determine that the device was not explosive.

No criminal charges are planned, and the driver and sole occupant of the car, whose parents live in Oregon, was turned over to the Canada Border Services Agency, said Paula Shore, a spokeswoman for the agency.

"It appears as though the male is suffering from a mental illness," Morrow said in the statement. "It is expected the individual will be returned to the border crossing, turned over to Canadian Immigration who in turn will ensure the safe return of the gentleman to the United States."

The episode closed Interstate 5 in the United States and Highway 99 in Canada at the busiest crossing between the two countries west of Detroit from about 9:30 p.m. to midnight, Shore said. Traffic in both directions was diverted less than a mile to the east to the Pacific Highway crossing.

Border officers checked the car after it entered Canada because the driver was acting erratically, Shore said.

"The driver was interviewed by border services officers, who were suspicious," she said. "They did a further search and found one or more than one suspicious package.

"We take safety and security very seriously."

Shore did not say precisely what about the driver drew the attention of Canadian border agents.

"Our border services officers are trained to look for inconsistencies," she added. "It's never just one thing that makes them want to take another look at someone."