A police dog checks the area before Prime Minister Mariano Rajoy arrives at a the scene of a train crash that killed at least 78 people
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Spain train crash: Investigation into cause

25 July 2013 Last updated at 19:57 BST

A judge has been appointed to investigate the cause of a train derailment in northern Spain, following reports that it could have been travelling much faster than it should have been.

Richard Westcott looks at some of the factors that the judge will be examining.