A driverless train smashed through two farm crossings and two level crossings, reaching speeds of 60mph, before derailing in Staffordshire.
Rail chiefs have begun an investigation into how the 120-ton runaway EWS freight locomotive, being used by Network Rail, careered for ten miles down the tracks before coming off the rails at Alrewas, near Lichfield.
Investigators are looking at whether the driver had left the brake off.
The incident happened at around 10.15am last Sunday on the line which had been closed to traffic while track repair work was carried out.
The Class 66 loco had been parked having been used to bring ballast to the site.
Eventually, the train, which is not thought to have been pulling carriages, reached a set of points and was derailed about five miles east of Lichfield.
An NR spokesman said: "The points would have prevented the loco getting on to an in-operation part of the main line, but this was obviously a serious incident, particularly as the loco passed through a number of crossings.
"The loco was moving over track that was downhill all the way, so it would have quickly gathered speed. We are looking into the incident with the help of EWS."
An EWS spokesperson said: "A locomotive was derailed at Alrewas following an unauthorised movement on Sunday, August 9 from an engineering site. "
