'Track dip' caused Carlton freight train derailmentContinue reading the main story
Rail investigators say a "severe track dip" caused a freight train to derail, closing the line for two weeks.
Bus replacements between Nottingham and Newark were brought in while a section of track at Carlton was repaired.
The Rail Accident Investigation Branch said examinations showed the dip was linked to a "large void in the ground".
Network Rail confirmed work had been carried out in the area by a third party in July and was not connected to the work at Nottingham station.'Inadequate line'
The derailment happened on 27 August, a day after Nottingham station reopened following five weeks of track and signal work.
A spokeswoman for Network Rail said: "A third party had been carrying out works in the vicinity of the level crossing in recent weeks which was not related to re-signalling work at Nottingham."
The Rail Accident Investigation Branch (RAIB) said the work in July had been to lay high voltage electrical cables under the level crossing.
It said its investigation would look at what caused the void and will include a review of the construction work that took place around the crossing.
The findings will be published at a later date.
Rail services between Nottingham and Newark resumed on Monday morning but business leaders say the line is still "inadequate" and have started a petition calling for investment.
Bob Poynter, from the Newark Business Club, said: "The train service is slow - the average journey time from Nottingham to Lincoln is 60 minutes. The fastest journey time is no quicker than it was in 1909.
"There are just three trains that get into Nottingham before 09:30 in the morning and for people who want to commute, that's just unacceptable."
The Department for Transport said it had advised Nottinghamshire County Council that it was able to allocate some of the locally devolved transport funds included in the Single Local Growth Fund, for investment in rail improvements between 2015 and 2020.