Updated

A South Dakota Highway Patrol trooper who stopped a speeding SUV towing a trailer discovered two box-spring mattresses stuffed with 89 pounds of marijuana.

Four California men were arrested Thursday and have been charged with drug distribution and possession.

The Rapid City Journal reported Saturday that the trooper initially pulled over Thai Yang, of Sacramento, Calif., for speeding along Interstate 90, east of Rapid City.

Yang was driving an SUV and towing a rented trailer, and gave the trooper permission to search the trailer, court documents say. A drug-detection dog found two box-spring mattresses stuffed with marijuana in several compartments.

Court documents say the pot was being taken to St. Paul, Minn. A second vehicle was stopped after authorities became suspicious of how its passengers were observing the initial traffic stop.

Yang and the three men in the second vehicle were arrested.

Earlier this week, Pennington County authorities stopped another man near Rapid City who was carrying 99 pounds of pot in his car.