Minister for Railways Sheikh Rashid says accident appears to have occurred due to human negligence.
The death toll from a fire in three bogies of a Tezgam train near Liaquatpur city jumped to 73 around 1pm, while many remain under critical condition, Rahim Yar Khan district government said on Thursday.
About 40 people, including women and children, were injured, Punjab Health Minister Dr Yasmin Rashid told AFP earlier.
The dead and injured are being shifted to DHQ Hospital in Liaquatpur. Some of the injured have also been shifted to Bahawal Victoria Hospital in Bahawalpur due to their critical condition.
The train was bound for Rawalpindi from Karachi. The fire was caused by a cylinder blast that occurred in the morning when some passengers were preparing their breakfast, Railways Minister Sheikh Rashid said, adding that they belonged to a tableeghi jamaat and were headed towards Raiwand.
Many people saved their lives by jumping off the train, the minister said.
In a video message, Railways Minister Rashid announced that a compensation of Rs1.5 million will be paid to the heirs of the deceased while Rs500,000 will be provided to those who are injured. He travelled to the scene of the incident and will meet families of the victims and the injured.
He said that two of the coaches that caught fire were booked under the name of the tableeghi jamaat's emir Hussain. The ministry, he said, was preparing a list of the victims. Rashid said that it was a "failure" on the part of the Railways authorities since they failed to carry out thorough checking of the passengers' luggage.
Later, in a press conference, the railways minister said that 134 trains had been making a minute-long stop for passengers in Raiwind. "The whole world earns from freight and we are the only ones who earn from passengers," he said, adding that the ministry was now earning upto Rs180-190 million versus the previous Rs130 million figure. "And then this tragedy unfolded."
Speaking about the tragic incident, Rashid said that the passengers who had been using the cylinder had been stopped by a guard and the driver from doing so. "In front of the guard they turned off the stove, but when he left, they turned it back on."
The railways minister thanked all those who participated in rescue operations especially Pak Army ambulances who saved many lives by transporting them quickly to hospitals.
Rashid rejected the impression that there was a non-availability of "pull chains" to alert the driver to stop the train. "The train stopped due to the chain being pulled, otherwise the whole train would have been on fire."
When asked about whether he will resign from the ministry, Rashid said he will speak about the matter on Sunday. He said an inquiry will be conducted within 15 days and the parties responsible punished.
The minister also paid a visit to the Shaikh Zayed Hospital in Rahim Yar Khan where some of the injured were being treated. He instructed the hospital staff to ensure the best possible treatment to all those wounded.
The minister will also pay a visit to Combined Military Hospital (CMH) in Multan.
Nabila Aslam, a railways official, told DawnNewsTV that the passengers must have "hidden the gas cylinder in their clothes" while boarding the train, as carrying one was strictly against the rules.
Rescue 1122 teams have extinguished the fire and are now carrying out a cooling and search operation under the supervision of Rashid. Army troops including doctors and paramedics were also dispatched to assist rescue teams in the operation, a statement by the Inter-Services Public Relations said.
An Army helicopter was also dispatched from Multan in order to rescue the injured, the ISPR statement added further.
Tezgam, one of Pakistan's oldest and most popular train services, runs between Karachi to Rawalpindi. The fare for a single journey from Karachi to Rawalpindi ranges from Rs1,750 for an economy seat to Rs7,650 for an AC Sleeper berth.
Prime Minister Imran Khan said he was "deeply saddened by the terrible tragedy of the Tezgam train".
"My condolences go to the victims' families and prayers for the speedy recovery of the injured. I have ordered an immediate inquiry to be completed on an urgent basis," he said via Twitter.
President Arif Alvi "expressed profound grief on the loss of precious lives in the tragic blast".
"Tragedy must immediately be investigated and accountability ensured," said PPP chairman Bilawal Bhutto Zardari. "PM should keep his pre-election promise and sack the minister until investigation is complete."
PML-N President Shehbaz Sharif said he was "heartbroken at such a massive train tragedy" and offered condolences to the bereaved families.
Human Rights Minister Shireen Mazari extended "prayers and condolences" to families of the victims of the "terrible Tezgam train tragedy".
In a tweet, Mazari regretted that the "tragedy [...] could have been avoided but ever since I can recall while travelling by train no baggage check or restrictions enforced. Tragic."
Jamiat Ulema-i-Islam (Fazl) Chief Maulana Fazlur Rehman issued a condolence statement and said that such events were a result of "poor planning". He demanded a thorough probe into the incident.
Leaders of Majlis Wahdat-e-Muslimeen, Pakistan Awami Tehreek and Millat-i-Jaferia Pakistan also extended condolences to victims' families and called upon authorities to ensure that the injured are provided with the best medical treatment and to hold a thorough inquiry into the incident.
An inquiry has been launched in the incident, APP quoted a senior official of the Railways Ministry as saying.
A notification was also issued by the Railways ministry's Rawalpindi division office soon after the incident directing police officials posted at stations as well as crew members, including guards, attendants, carriage staff etc. to ensure that no gas cylinder is allowed on board trains.
"It will be the joint responsibility of the running crew to confiscate gas cylinders being used by the passengers in running trains," the notification said.
"[Staff] on stations must have a joint responsibility to keep watch on the activities of the passengers and in case any unusual thing is happening, [they] must report it for timely eradication."
In July, a train collision in Sadiqabad between passenger train Akbar Express and a freight train had killed more than 20 and injured more than 80 people.
In June, three people were killed when a passenger train, the Jinnah Express, hit a freight car near Hyderabad. At the time, Rashid had accepted responsibility and sought an apology from the nation.
"I accept responsibility for this accident and seek an apology from the nation. Such a portfolio is not important for me as I have become federal minister for the eighth time. And I will resign whenever I feel burden on my conscience," the minister had said at the time.
Additional reporting by Javed Hussain.