By Al Goodman. Elwyn Lopez and Catherine E. Shoichet, CNN

Madrid (CNN) — A passenger train crash in northwestern Spain Wednesday killed more than 56 people and injured more than 100, a regional official said.

Agustin Hernandez Fernandez of the Galicia infrastructure ministry said more than 20 injured victims remained in critical condition early Thursday.

Investigators are looking at all possible causes of the crash, a senior aide to Spain’s prime minister said Wednesday; their initial assessment is that it likely wasn’t the result of terrorism. 

Pictures of the scene showed at least one train car snapped in two and another one of the train’s cars on fire. Rescue crews and fellow passengers pulled out bodies through broken train windows as stunned survivors looked on. Police escorted bloodied passengers from the wreckage.

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