A single-vehicle crash early Sunday in rainy weather on Highway 128 in Mendocino County injured one man seriously, the CHP said.

According to CHP, a 1994 Dodge Ram driven by Eddy Joseph Jones II, 54, of Navarro, was eastbound at mile marker 38 at an unknown speed when it ran off the road and hit a tree about 2:20 a.m.

Jones, who was wearing a seat belt, suffered minor injuries.

His passenger, Luis Armando Borja Jr., 56, of San Francisco, was not wearing a seat belt, and was thrown from the truck, suffering major internal injuries.

The cause remains under investigation. Alcohol and drugs are not believed to be a contributing factor.