Officers were called to the railway line in Tonge, near Sittingbourne, shortly after 12.45pm on Sunday following reports of a train striking a van, British Transport Police said.
Paramedics also attended, but the person died at the scene.
The incident is currently under investigation, with no services running through the area.
Footage shared on social media appeared to show a large fire producing black smoke in a rural area lined with trees, while other images showed helicopters landing on fields next to the railway line.
David Davidson, chief operating officer at Southeastern Railway, which runs services on the line, said: “A train was involved in a collision with a van at a level crossing near Teynham earlier this afternoon.
“We are working with the emergency services and the Rail Accident Investigation Branch (RAIB) following this incident.
“Passengers on the train involved have been transferred on to another train and taken to Sittingbourne for onward travel.
“Trains are currently unable to run through the area and replacement buses are currently running between Gillingham and Faversham and Sittingbourne and Sheerness-on-Sea.”
Mr Davidson said ticket acceptance was in place on other Southeastern high-speed trains, Thameslink and Fast Track buses between Gravesend and Ebbsfleet to help customers complete their journeys.
He added the rail operator was working with the RAIB to understand the cause of the incident and reopen the line “as soon as possible”.
Kent Police said it was called to a report of the collision at a level crossing in Lower Road, Teynham, at 12.43pm, and that patrols remain at the scene.
South East Coast Ambulance Service and Kent Fire and Rescue Service also attended the incident.
