California Highway Patrol investigators are trying to find witnesses to a Feb. 7 overnight crash near Pleasanton that killed a Salida man.

Officers suspect 55-year-old David Leon Davis might have suffered a medical problem before he drove off the roadway near the intersection of Sunol Road and Castlewood Drive in unincorporated Alameda County.

CHP Officer Tyler Hahn said investigators need to speak with anyone who saw the car leave the road.

"There were no evasive marks left on the roadway or dirt shoulder that would indicate braking, swerving, etc.,” Hahn said.

Passing motorists spotted the 2014 Volkswagen Jetta wagon about 20 to 30 feet off the road about 8:10 a.m. The car sustained front end damage and overturned, coming to rest on its roof.

Davis was inside and pronounced dead at the scene.

Investigators do not know what happened or when, but suspect the car hit one or more trees before flipping over. The car's engine was cold when the vehicle was found.

"Unfortunately, because the vehicle left the roadway in the dark and ended up behind a small dirt embankment covered in foliage, there may be no witnesses," Hahn said.

An autopsy will examine whether the driver had a medical issue and determine whether he was under the influence of alcohol or drugs. Hahn said it also is a possibility he fell asleep at the wheel.

"These types of crashes are sad for the family because without a witness, and without a statement, sometimes there is still a question of why," Hahn said.

Anyone with information was asked to call the CHP office in Dublin at 925-828-0466.

Salida is located about seven miles from Modesto, off Highway 99.