A Casper man died in an accident on Thursday morning involving two tanker trucks on Interstate 25 about eight miles south of Kaycee, according to a press release from the Wyoming Highway Patrol.

Alexander P. Osborn, 53, was driving on an uphill grade on southbound on I-25 in a 2007 Kenworth tractor trailer/tanker combination, which was pulling a pup trailer.

Osborn was following Father John Boydston, 68, who was driving a two-door 1983 Oldsmobile pulling a 16-foot, single-axle house trailer.

Both rigs were hauling hot road oil and traveling about 50 mph.

For unknown reasons, Osborn drove into the rear of Boydston's rig. The impact caused the drivers to lose control of their vehicles, which went off the highway's west side and down a 20-foot ravine.

Osborn's rig rolled one-fourth onto its driver's side. The pup trailer remained on the highway, but also rolled by one-fourth and came to rest on the bridge deck over the South Fork of the Powder River.

Osborn was taken by helicopter to the Wyoming Medical Center, and Boydston was taken by ground ambulance to the hospital, too.

Wyoming Highway Patrol troopers estimated about 4,500 gallons of the road oil leaked from the tanker compartments. The oil was about 800 feet from the river.

Both lanes of southbound I-25 were closed for about 1 1/2 hours during the investigation and cleanup. Southbound traffic was detoured at the TTT interchange.

The trucking company is responsible for cleanup of spilled road oil and will be using the right of way to clean the area affected by the spill.

Both drivers were wearing seat belts.