A 10-car Burlington Northern Santa Fe Railway train traveling from Richmond to Barstow derailed at about 1:30 a.m. near Loveridge Road in Pittsburg, BNSF spokeswoman Lena Kent said.
The incident has affected Amtrak service in both directions, she said. "It's a single main line and nothing can get through there."
Nine of the 10 cars were empty, she said. The 10th contains liquid petroleum gas, but Kent said the car and its contents were not damaged.
"It was moving at a very slow speed," she said. "It was actually backing up when it derailed."
The car containing the liquid petroleum is not completely on the ground, but is leaning at a 45-degree angle, she said.
No one was injured in the derailment and BNSF crews are at the site investigating the cause, Kent said.
There is no estimate for when the tracks will be cleared, she said.
The incident is disrupting Amtrak service on the Oakland-to-Bakersfield corridor, spokeswoman Vernae Graham said. Passengers are being bused between the Martinez and Stockton stations, she said.
Graham said Amtrak has 10 trains scheduled along that route today.