Authorities are questioning a truck driver involved in a crash with a commuter train that injured 28 people northwest of Los Angeles.

Scott Johnson, a spokesman for the Metrolink system whose train struck the truck at around 5.44am local time, said police in Oxnard found the driver and questioned him. Three cars of the five-carriage Metrolink train tumbled on to their sides in agricultural country 104 kilometres northwest of Los Angeles.

Little was left of the truck, which stopped at a marked crossing. Some debris was in a nearby intersection and some close to the tracks.

Fire officials say four of the 28 injured are in critical condition.

Twenty-three people were unhurt.

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