A 25-year-old Napa man was hospitalized Thursday after the flatbed truck he was driving ran off the road and struck a tree near St. Helena.

Jacob LaPierre was in critical condition at Queen of the Valley Hospital, where he was taken after the 1 p.m. crash on Silverado Trail north of Taplin Road.

LaPierre was driving a 1995 Ford flatbed truck when, for reasons still under investigation, it traveled off the roadway, rolled onto its right side and collided with a large oak tree, the CHP said.

The truck's engine compartment caught fire, but flames were extinguished by a passerby with a fire extinguisher. Emergency personnel extricated LaPierre.