At least 46 passengers died when a train travelling from the Pakistani city of Karachi to Lahore caught fire, police say.
Local media said the fire was caused by the explosion of a gas cylinder being used by passengers cooking food.
The blaze is thought to have spread to at least three carriages.
According to officials cited in local media, many of the victims died as they tried to jump off the burning train.
Another 30 people have reportedly been injured and officials say the number of dead may still rise.
“Two cooking stoves blew up. They were cooking, they had (cooking) oil which added fuel to fire,” Sheikh Rashid Ahmed, minister for railways, said.
Passengers bringing stoves onto trains in order to cook meals on long journeys is a common problem, the minister added.
The accident happened near the town of Rahim Yar Khan in the south of the Punjab province.