Scottish leader Nicola Sturgeon said the derailment of a train near Stonehaven on Wednesday morning was "extremely serious", as video footage on social media showed smoke rising from the scene on the east coast of the country.
"This is an extremely serious incident," she said. "I've had an initial report from Network Rail and the emergency services and am being kept updated. All my thoughts are with those involved."
Police received reports of a train derailing near Stonehaven, a town 15 km (9 miles) south of the city of Aberdeen, at 0940 a.m. on Wednesday.
"Emergency services are currently in attendance and the incident is ongoing," a Police Scotland spokeswoman said.
British Transport Secretary Grant Shapps said he had been briefed on the incident.
A photograph on Twitter showed an air ambulance in a field near the scene where smoke was billowing from a woodland area, alongside about 25 police vehicles and ambulances.
Local reports said there had been flooding in the area overnight.