A dirt biker had driven over something numerous times, not knowing what it was, but on Saturday he saw the words "highly explosive" on what would turn out to be partially buried seismic explosives, said Burleigh County Sheriff's Capt. Collin Rixen.

Rixen said the biker, driving in the "Desert" recreation area south of Bismarck, told deputies the explosives had been there for a long time, had seen them many times, but had never realized what they were.

Sheriff's deputies did know and called in the Bismarck Police bomb squad to take care of them.

Rixen said the 4-foot-long sticks, used by seismographers during oil exploration work, didn't have blasting caps and won't explode without the caps.

He said there's no way of knowing if there could be more explosives in that area or not. Rixen said the explosives that were found looked to have been left there "quite a while ago," he said.