No further investigation can be justified into a train derailment at Stonehaven that disrupted rail services between Aberdeen and Dundee for two days, a report has said.
The line had to be closed north of Dundee after two of three carriages derailed during a low-speed move on 10 October.
No-one was injured as a result.
The Rail Accident Investigations Branch (RAIB) said it had ruled out various areas as potential causes.
These included the condition of the track and signalling infrastructure, the train itself, or the way it was being driven.
However the RAIB concluded that the "potential for safety learning is insufficient to justify further investigation".
The RAIB said it would share evidence with the railway industry parties involved to assist with their own investigations into the incident.
The driver and guard were the only people on board the train when the derailment happened at between 12mph and 14mph.
Replacement bus services had to be used during the disruption.