Police investigating the derailment of a train are trying to trace four youths seen near the track the night before the incident.
The front wheels of the 8.04am CrossCountry train between Edinburgh and Aberdeen came off the tracks at Inverkeilor, between Arbroath and Montrose in Angus, at 9.45am on Sunday November 4.
It forced First ScotRail, which runs most trains in Scotland, to put on alternative transport for some passengers on Sunday and Monday, with many routes to Aberdeen ending at Dundee and replaced by buses.
None of the 36 passengers on the derailed train were injured but the 49-year-old driver was treated for a minor head injury.
British Transport Police (BTP) previously said they believe the object that derailed the train was put on the track deliberately and a £25,000 reward has been offered by the rail industry to anyone who can help police find those responsible.
Officers want to speak to four youths seen in the area at about 7.30pm on the night before the incident.
The group range in height from 5ft to 5ft 6in and one was wearing a grey or light-coloured hooded top and trousers, BTP said.
Detective Chief Inspector Iain Miller said: "The youths were seen walking towards Bryanton House just off the A92.
"This would have been prior to the bonfire at Inverkeilor, the night before the incident occurred. It is important to trace these youths in order to eliminate them from our enquiries."
BTP also want to speak to anyone who was at the bonfire and asked anyone who took photographs on the evening to contact them on 0800 40 50 40 or anonymously via Crimestoppers on 0800 555 111. Tayside Police are assisting in the investigation.