On July 6, 1978, fire burned out a British Rail sleeping car at Fairwater Close, Taunton, killing 13 people and injuring others.
The train was travelling from Penzance to Paddington station in London when laundry stacked against an electric heater ignited, the BBC said.
All 31 of the dead or injured were in the front two carriages.
Car doors were locked, a violation of British Rail rules, preventing a means of escape.
A passenger said: "I remember being woken up and being carried out of the train. The place was full of smoke. All I could see was people smashing the windows and trying to get other people out."
Ray Stokes, a newspaper reporter, said people living near the tracks used wire cutters to break down a fence to render aid.