A man who was struck and killed by a tractor-trailer rig north of Ukiah on Thursday morning was a transient living between the Ukiah and Willits areas, the Mendocino County Sheriff's Office said.

Kenneth Mark West, 26, died when he was struck on North State Street near Kunzler Ranch Road around 9 a.m., the CHP said.

The three-axle semi left the area, and authorities are investigating the case as a possible hit-and-run crash, though it was unclear if the driver knew someone had been hit.

Authorities were unable to say whether there was a link between the death and the southbound big rig detained later Thursday morning at a brake-check station near Cotati. Officers reportedly were still investigating the truck at mid-day, though no additional information was available, the CHP said.

West's death is similar to an ongoing trend in Santa Rosa, where seven people have died since January after being struck by vehicles.

Four of them were homeless people, authorities said.