A truck driver hauling roughly 50 tons of rice straw for Rim Fire recovery efforts was killed Friday morning when his big rig went off the Clavey River Bridge.

California Highway Patrol received a call about the accident at 10:52 a.m. Jason Austin was the first CHP officer to arrive at the scene and said witnesses reported there appeared to be a mechanical problem with the truck's brakes before it went off the bridge on Cottonwood Road.

Austin said witnesses were following in a vehicle behind the deceased man's truck at about 40 mph going east to unload the straw. The Rim Fire's Burned Area Emergency Response team has been working the past two weeks to complete it's final project, aerial mulching, which involved the straw being spread over the charred landscape from helicopters to help prevent soil erosion during winter storms.

The witnesses told Austin that the truck's brakes began smoking and it started to "pull away" from them. The truck then entered a right-hand curve to get on the bridge but went through the guard rail and plummeted about 150 feet to the river floor.

Tuolumne County Sheriff's Coroner Rob Lyons arrived about an hour later and was withholding information about the driver's identity until he personally notified the man's family.

The driver worked for Gigli Hay Inc, a Lathrop-based company that is under contract with the U.S. Forest Service to provide the straw for aerial mulching. A truck hauls about 50 bales of straw, which weigh about 1-ton each, on a double-axle flatbed trailer.

Forest Service personnel closed the road to through traffic while the Tuolumne County Search And Rescue Team worked to remove the man's body from the wreckage. The road has been closed to the public before the bridge and was open only for loggers and contractors working on the BAER team's aerial mulching project.

California Fish and Wildlife Warden Darren Walther responded as well, because gasoline and oil from the truck was reportedly spilling into Clavey River, which feeds into Don Pedro Reservoir. He said the recent rains have raised the river's level to the point where it was unlikely the department would be able to contain and vacuum the spill.

Most trucks that size feature two gas tanks containing between 100 and 200 gallons of gasoline each, Walther said, but he didn't think the amount that spilled would have any "huge environmental impacts" on the river.

Burned Area Emergency Response Team Leader Tom Beddow was in Sacramento International Airport waiting for a flight home when he was contacted for comments Friday afternoon.

The accident happened just prior to Beddow leaving the area after spending 55 days overseeing emergency projects to stabilize soil and repair roads that were damaged by the Rim Fire.

Beddow said he's been a BAER team leader since 2007 and this was the first fatality that's happened during post-fire aerial mulching operations.

CHP Officer Nick Norton said crews left the scene about 4 p.m. and were going to attempt to tow the truck from the canyon Saturday morning. He said the road on each side of the bridge would likely be closed while they were at work, but he didn't have an exact time.