Investigators probe Amtrak train derailment that killed three

The scene of the derailment in Montana (Kimberly Fossen via AP)

A team of investigators has been sent to the site of an Amtrak derailment in Montana in which three people died and seven people were hospitalised, officials have said.

The westbound Empire Builder was travelling to Seattle from Chicago when it left the tracks at about 4pm on Saturday near the small town of Joplin.