GENEVA (AFP) - A Swiss train derailed on Wednesday in the mountainous eastern region of Graubuenden, Switzerland's ATS news agency reported.

ATS said that Graubuenden police said the accident was "serious", but that officers had not provided further details.

Contacted by AFP, police said that they could not comment immediately.

ATS said the train, from the regional rail company Rhaetischen Bahn, had derailed near Tiefencastel on the line between the city of Chur and the resort of St. Moritz.