A police officer is in a critical condition in hospital after being hit by a train as he attempted to save a distressed man on the tracks.
Nottinghamshire Police were called to a residential area in Balderton at about 19:00 BST on Thursday over concerns for a man's safety.
The force said one of its officers was hit by the train during the incident, while a man suffered non life-threatening electrocution injuries.
They both remain in hospital.
British Transport Police (BTP), which is leading the investigation, said it happened on the line near Newark Northgate station.
"Officers attended alongside paramedics, where one man was found to have sustained non life-threatening electrocution injuries, and another man, a Nottinghamshire police officer, had sustained life-changing injuries and sadly remains in a critical condition," a BTP spokesperson said.
"British Transport Police is continuing to make inquiries into the incident."
Nottinghamshire Police said the injured officer had been taken to the Queen's Medical Centre in Nottingham.
Chief Constable Kate Meynell said: "This is a truly devastating incident that has left one of our officers very poorly in hospital. We are supporting his family and ensuring that he gets all the care and support he needs.
"This was also extremely traumatic for all those who attended the scene, some of whom provided immediate medical assistance while the ambulance was on its way.
"I would like to personally thank them for their quick and dedicated response to this incident."
Simon Riley, chair of the Nottinghamshire Police Federation, said the organisation's thoughts were "very much with our injured colleague and his family".
He added: "We are supporting a number of officers involved in the incident and will continue to do everything we can to support all of our members at this time."
Nottinghamshire Fire and Rescue Service also expressed sympathy for the officer.
In a post on X – formerly Twitter – a spokesperson said: "Our thoughts are with the family, friends, and colleagues of our fellow emergency responder."
Newark MP Robert Jenrick added: "Risking your life to save someone else is the epitome of public service.
"I'm humbled by the bravery and self-sacrifice of the police officer who was critically injured at Newark station today, in the line of duty.
"He is a true hero and I know the whole community will join me in sending our thoughts and prayers to him and his family."
Follow BBC East Midlands on Facebook, on Twitter, or on Instagram. Send your story ideas to eastmidsnews@bbc.co.uk.
British Transport Police
Nottinghamshire Police
Drug dealer caught with nunchucks and a pistol in Radford Nottingham
Hucknall shoplifters in court marks success for Business Crime Forum
Police presence has an immediate impact on crime in town centre
Chance to learn more about police and fire service at Mansfield community event
Hucknall man sent to Crown Court to face rape charges
Support for Syrian, Afghan and Ukrainian refugees lauded at meeting
Russian space base possible venue for Kim-Putin talks
Putin and Kim: Friends in need (of ammunition)
US takes on Google in fight against tech giants
Why mobile saunas are being sent to Ukraine's front line
'We need help from whoever will give it'
Inside Kim Jong Un's luxury bulletproof train
Three minutes to the centre of the Earth. Video
What is Ethiopia's giant dam on the Nile?
Robots are trained to help revive coral reefs
Putin and Kim: Friends in need (of ammunition)
Queen of African horror: I am terrified of ghosts
US takes on Google in fight against tech giants
Florida's first hurricane-proof town
The greatest spy novel ever written?
Why is everyone crazy about Aperol?
© 2023 BBC. The BBC is not responsible for the content of external sites. Read about our approach to external linking.