Three people have died in a train derailment in Aberdeenshire and six people are injured, British Transport Police (BTP) have said.
The force said those pronounced dead at the scene near Stonehaven include the train's driver.
The 6.38am Aberdeen to Glasgow Queen Street ScotRail service crashed on Wednesday morning amid heavy rain and flooding.
BTP said those injured have been taken to hospital and are not thought to be seriously hurt.
The force believes all passengers have now been accounted for.
BTP chief superintendent Eddie Wylie said: "This is a tragic incident and first and foremost our thoughts are with the families and friends of those who have very sadly died this morning.
"We remain on scene alongside our emergency service colleagues and a major incident operation has been under way.
"I would like to reassure the public that this was not a busy service and from CCTV inquiries and witness statements we believe all passengers have been accounted for."
He added: "However, once the area has been made safe then a full and thorough search will be conducted, which is likely to take some time.
"I know many people will understandably have questions and we will be working closely alongside the Rail Accident Investigation Branch and the Office of Rail and Road to establish the full circumstances of how the train came to derail."
Rail industry sources told the PA agency the suspected cause of the incident is a landslip.
They said the train stopped due to a landslip and moved back along the line when it crashed into another landslip.
The train comprised a locomotive and four carriages.
It is understood the locomotive and three carriages derailed and slid down an embankment.
Dozens of emergency service vehicles, including an air ambulance, were called to the scene at about 9.40am.
Unions called the crash a "tragedy" as a major incident was declared at Aberdeen Royal Infirmary.
Speaking before First Minister's Questions on Thursday, Nicola Sturgeon said: "My immediate thoughts and the thoughts of those across the chamber are with all those involved."
She later tweeted the NHS Grampian helpline number: "Anyone worried about friends or family involved in the Stonehaven rail incident can call 01224 319519 for advice and support."
Ms Sturgeon is holding a Scottish Government resilience meeting on Wednesday afternoon.
Local MP Andrew Bowie said he had spoken to the UK's Transport Secretary Grant Shapps, who is liaising with Network Rail Scotland and ScotRail about the derailment.
He told PA: "It's obviously a terrible situation, a train derailment, the emergency services are on the scene."
Prime Minister Boris Johnson tweeted: "I am saddened to learn of the very serious incident in Aberdeenshire and my thoughts are with all of those affected. My thanks to the emergency services at the scene."
Train operator ScotRail posted a message on Twitter shortly after 6.30am warning services across Scotland would be disrupted due to "extremely" heavy rain and flooding.
Video posted to social media by Network Rail Scotland showed a landslip on the track at Carmont, believed to be close to the scene of the crash.
It is unclear whether the landslip was directly related to the derailment.
Network Rail tweeted at 9.49am: "At Carmont, we've had reports of a landslip, which means services can't operate between Dundee & Aberdeen."
Police had said reports of the train derailment were first received at 9.40am.
NHS Grampian has set up a "welcome centre" at Midstocket Parish Church in Aberdeen for those impacted by the crash, staffed by the health board's chaplains.
Mick Lynch, the assistant general secretary of the Rail, Maritime and Transport union said: "The facts behind this incident will need to be established in due course but at this stage we are focused on support and assistance and our thoughts are with all those impacted by this tragedy."
Paul Plummer, chief executive of the Rail Delivery Group, which represents the rail industry, said: "We are saddened to learn about the incident in Aberdeenshire today and our thoughts are with those affected.
"While an investigation will follow, our current focus is to provide every support we can in the immediate response."
The last time a train driver was killed in a crash on Britain's railways was in Berkshire in November 2004, the Office of Rail and Road said.
Seven people died when a train collided with a car that had been deliberately driven on to a level crossing at Ufton Nervet.