Police pulled over a vehicle on an interstate highway because it was travelling too slowly and found 500 pounds of marijuana inside.

After suspicions were aroused, officers followed the Toyota Tundra pickup truck travelling east on the interstate highway on Interstate 94 in southeastern North Dakota.

Stutsman County sheriff Chad Kaiser said the truck was driving below the speed limit, so the deputy began following it.

The deputy saw a faster vehicle pass the truck and pull back into the travel lane. The pickup truck did not slow down and was driving too closely behind the passing vehicle.

Authorities arrested Nhia Lee, 36, of St Paul, Minnesota and Bee Thor, 37, of Oshkosh, Wisconsin after searching their vehicle on Sunday (21 January) just after 9am and finding 470 heat-sealed bags holding 476 pounds of marijuana.

During their initial appearance at Southeast District Court Monday (22 January), the men applied for public defenders. Lee and Thor were charged with possession of a controlled substance with intent to deliver, marijuana, a Class A felony, and possession of drug paraphernalia, marijuana, a Class A misdemeanour.

The two men are being held in the Stutsman County Correctional Center with bail set at $200,000 each. According to Grand Forks Herald, a sheriff's deputy made a similar arrest near Jamestown on 13 December.

A deputy discovered 198 1/2 pounds of marijuana being transported in a minivan by Mae Thao, 31, of St Paul and Xang Thao, 30, of Redding, California. The vehicle was pulled over during a traffic stop around nine miles east of Jamestown.

The Thaos remain in the Stutsman County Correctional Center with bail set at $500,000 each.

Kaiser expressed concern over the large amounts of marijuana being transported through the Jamestown area. "It is unusual and very concerning to me that this amount of marijuana is moving through our community," the sheriff said.