The California Highway Patrol says the truck collided with a freight train at Fourth and Grangeville Avenue east of Hanford, about 17 miles from the Amtrak accident scene.
The driver of the big rig may have suffered injuries in that accident but it's unclear how serious those injuries are.
The Amtrak derailment call came in to 911 just before 12:30 p.m. on Monday.
The Kings County Assistant Sheriff said the Amtrak train was traveling south when a collision occurred with a truck on Kansas Avenue near Hanford.
An Amtrak official said there were 169 passengers on the train plus 4 crew members at the time of the crash. The sheriff's department estimated that 30-50 people suffered injuries. The California Highway Patrol said there were no serious injuries, but one small child was hurt.
About 80 emergency personnel treated victims at the scene, according to the Sheriff's office.
The Adventist Medical Center in Hanford set up a command center, according to a hospital spokesperson.
The train was bound for Bakersfield coming from Oakland.
Uninjured passengers were transported by bus to the Civic Auditorium in Hanford. Those who wished to continue on to Bakersfield were taken by Amtrak bus.
This is not the first time a crash involving an Amtrak train has taken place at this location. In May 2008 a train collided with a truck carrying lemon peels and derailed a train car, injuring about 20 people. Also in August 2007, another crash involving an Amtrak train happened at the same intersection. In that crash, the train was able to slow before hitting a vehicle, but the family inside the car was hospitalized.