Authorities suspect an electrical short circuit may have caused the fire.
At least 50 people have died after a fire swept through a moving train bound for the southern Indian city of Chennai, local officials say.
The fire was discovered at a railway station in Nellore, in Andhra Pradesh state early on Monday, Sri B Sreedhar, the local administration chief, said.
The blaze has been extinguished and at least 22 injured people have been hospitalised. The coach was completely gutted, with rescuers forced to use gas cutters to access parts of it.
Sreedhar said the fire was believed to have been caused by a short circuit in the coach, though a railways ministry spokesman said it may have been caused by "someone carrying inflammable materials on the train".
After the fire was discovered, Sreedhar said, the stricken section was detached from the rest of the train to prevent the blaze from spreading.
Accidents are common on India's immense state-owned rail network.
In May, 24 people were killed when a passenger train crashed into a goods train, also in Andhra Pradesh state.
Train accidents in India have killed 1,220 people over the past five years, railway officials recently revealed.
India's railway operates 9,000 passenger trains and carries some 18 million passengers every day, connecting every corner of the country.