The crash in Cantabria occurred at about 6:30 p.m. Friday on the line between Cabezon de Sal and Santander, ThinkSpain reported. The train was on a stretch of track with a steep cliff above it on one side and the River Saja on the other.
Investigators said they believe the derailment was caused by rocks swept down the cliff to the track by recent heavy rains. Two cars fell over, including one that was stopped from tumbling into the river by trees that broke its fall.
One passenger suffered serious head injuries and two had multiple broken bones, officials said. Four were treated at the scene for minor injuries and seven were taken to a hospital.