The collision involving Metrolink's OC Line 681 occurred around 5:30 a.m. at an intersection in the Los Angeles-area suburb of Santa Fe Springs. The train's crew and around 120 passengers were evacuated.
Four people on the train complained of pain and were treated at the scene. It was not clear why the RV was stopped on the tracks or how fast the train was moving.
“Our engineer went into emergency stop procedures but unfortunately was unable to stop in time,” Metrolink spokesman Scott Johnson said.
The RV, Metrolink train and a nearby freight train stopped on a parallel track caught fire, authorities said. The flames charred a rail car on the freight locomotive and the RV was destroyed.
Passenger Ryan Hajek said he felt the train operator slam the brakes as it approached the intersection.
“The lights inside went dark, so we knew something went wrong, I knew we crushed into something," Hajek told KABC-TV. "As we stopped, I saw all the debris of what looked like a car on the side of the tracks, and I knew then that we had hit something."
Police were looking for four people seen running from the tracks just before impact, Whittier Police Officer Hugo Figueroa said.
Buses were called in to transport passengers to Union Station in Los Angeles. Metrolink said passengers on trains 681, 601, 603, 701 and 700 with a valid fare can receive up to a $50 reimbursement for alternate transportation.
The Associated Press contributed to this report.