MORONGO VALLEY — The driver of tractor-trailer hauling an oversized generator died when he was thrown from the cab Wednesday night on Twentynine Palms Highway.The victim, a 44-year-old man from Prunedale, was driving a 2017 Western Star commercial truck with a 120-foot trailer hauling a generator east on Twentynine Palms Highway. He was part of a convoy with two other Western Star tractors, all being escorted by CHP vehicles because the generator was an oversized load. They were headed from Beaumont to Arizona.According to the CHP, around 10:05 p.m. east of Fobes Road, the driver in the lead tractor began to drift south toward the dirt shoulder. The tractor jackknifed, then ran into a wooden property fence next to the highway. Possibly because of the collision, the side-saddle fuel tank on the left side of the truck ruptured, spilling about 120 gallons of diesel fuel on the dirt shoulder and private property, a CHP report states.Sometime during the collision, the driver was thrown from the tractor and was killed.His name has not been released by authorities.Both eastbound lanes of the highway were closed for hours after the crash, and by Thursday afternoon, the CHP and Caltrans still had one of those lanes closed while a hazardous materials crew operated a truck that sucked up the diesel-soaked sand.The victim’s tractor, registered to Barnhart Crane and Rigging Co. in Long Beach, and the oversized generator remained on the scene.“Our major concern now is opening up traffic,” Sgt. N. Salais, the CHP officer in charge of the scene, said around noon Thursday.