Railway Minister Sheikh Rashid Ahmed told Geo TV: "Two kitchens exploded, cooking, cooking oil, adding fuel to the fire."
He added: "Most deaths are due to people who jumped off the train".
Authorities said many more people are injured, some in critical condition.
Dr. Yasmin Rashid, Punjab's Minister of Health, told AFP that more than 40 wounded had been transported to local hospitals.
The authorities warned that the death toll could increase further as the army was recruited to help with the rescue.
The minister said that people who prepare meals on long train journeys are a common problem.