Tracy Police say the first officer to arrive reported a man and woman inside the truck who looked suspicious. When the officer searched the truck, he found an explosive.
The first pipe bomb was found near Highway 50 and Stockton Boulevard last month, and the second was found on Monday on the northbound Arden Way exit of the Capital City Freeway. The California Highway Patrol say there is little doubt that the two devices were set there on purpose.
The California Highway Patrol is looking for a suspect who planted a pipe bomb along Highway 50 in Sacramento on Wednesday.
A woman who was arrested in a Lodi parking lot on shoplifting charges Monday also had two pipe bombs in her car, police say.
A bomb scare brought busy roads in Stockton to a close for about five hours on Thursday.
Explosions in a neighborhood got police on edge after possible pipe bombs were found in Ceres.
Authorities say one person was injured when a pipe bomb disguised in a newspaper exploded at a residence in a San Francisco Bay area suburb.