Three of the carriages of Tezgam Express caught fire at Talwari Station near Rahim Yar Khan, killing at least 73 passengers and injuring more than 40.
Emergency alerted in hospitals across the district.
The railways minister, Sheikh Rashid Ahmed, said the incident was caused by the explosion of a gas cylinder passengers were using to cook breakfast on the train.
The minister said that most of the deaths were passengers throwing themselves from the moving train due to the fire.
The Tezgam Express was traveling from Karachi to Rawalpindi city of Pakistan.
After the incident the railway authorities of Balochistan have banned gas cylinders in trains departing from Balochistan’s capital, Quetta.
Passenger are advised not to carry any such material in trains which can cause fire.
Incidents on trains are common in Pakistan, where corruption, mismanagement and lack of investment have caused the railways to decline over the past few decades. Overcrowding is also a frequent safety issue, The Guardian News reported