The Rail Accident Investigation Branch (RAIB) has formally launched an investigation after a rake of 22 wagons ran away from a sidings at Old Bank sidings at Toton, Nottinghamshire.
The incident happened in the early hours of the 17th January and saw the rake run out of a siding and passed a red signal generating an alarm at the East Midlands Control Centre.
After passing another red light, the wagons, which weighed around 1870 tonnes, derailed at a set of trap points at Toton South after a distance of about 1/2 mile.
No one was injured in the incident.
The RAIB says that it will now carry out an investigation to identify the sequence of events which led to the accident and what could have been done to prevent.