Officials said they had located a previously unreported train undercarriage down a gully near the site of a train crash in Spain that killed 42 people. Experts said the finding could help investigators clarify what caused the disaster.

Ignacio Barron, head of Spain's Commission of Investigation of Rail Accidents (CIAF), said on RTVE: "What always plays a part in a derailment is the interaction between the track and the vehicle, and that is what the commission is currently [looking into]."

Rescuers were trying to gain access to the worst-hit carriages in one of Europe's deadliest train crashes that left at least 41 dead.