BBC Report:
More than 140 were hurt, 36 seriously, after all eight carriages of the Madrid to Ferrol train came off the tracks near Santiago de Compostela.Media reports say the train may have been travelling at more than twice the speed limit around a curve.
Officials say one of the train's drivers has been put under formal investigation.
It is one of Spain's worst ever train crashes. PM Mariano Rajoy has declared three days of national mourning.
"Today is a very difficult day. Today we have lived through a terrible, dramatic accident, which I fear will stay with us for a long time.
"For someone from Santiago, like myself, believe me, this is the saddest Day of Saint James of my life."
Two investigations are being carried out - one judicial, the other by the investigative commission for rail accidents, under the Ministry of Public Works, Mr Rajoy added.