A 72-year-old man and a 15-year-old boy have died after a car was struck by a train at a level crossing.
Emergency services were called to the Barns Green crossing in Emms Lane, Horsham, West Sussex, at 08:47 GMT.
The two victims – the car driver and passenger – are believed to be grandfather and grandson. No-one on the train was hurt.
British Transport Police (BTP) said their family was being supported by specialist officers.
Det Insp Brett Walker said: “This is an extremely tragic incident and our thoughts are with the family at this difficult time.
“Our officers have been working at the scene, and will continue to do so for the rest of the day, to ensure we gain as much information about how the collision happened.”
Southern said rail services would be affected for the rest of the day, with buses replacing trains between Horsham and Pulborough.
BTP officers, who worked alongside Sussex Police, said the two victims were pronounced dead at the scene.
Paramedics said they walked through the train after the collision to check on passengers and ensure no-one was injured.
The Rail Accident Investigation Branch has been informed.
Many of the train passengers were taken to the nearby Sumners Ponds campsite, where they were given hot drinks.
Two of them, Sinitta and Beverley, told BBC Sussex there had been a fire after the crash.
“The train stopped suddenly and then people started screaming,” they said.
“Then we saw the fire so we moved up the train, and they evacuated the train.”
‘Plume of smoke’
Sumners Ponds staff put a message on the local village Facebook page, appealing for people to give the passengers lifts to Horsham station.
Campsite manager Matt Gale described seeing two trains at the level crossing as he arrived for work and a huge plume of smoke.
He said the last of the train passengers left on coaches just after 11:00.
He estimated they had looked after about 100 people.