ISLAMABAD, Pakistan — When a tanker truck overturned on a road in eastern Pakistan on Sunday, hundreds of people rushed toward the vehicle to collect the spilled and leaking fuel.
Using buckets, bottles and cans, they scooped up some of the 5,500 gallons of fuel that was gushing onto the road. For about an hour, men, women and children from nearby villages, as well as some passers-by who pulled over in their cars and motorbikes, collected the windfall, despite attempts by the police to warn them away from the scene.
Then, suddenly, the truck caught fire and exploded, killing at least 150 people and seriously injuring at least 100 others.
At least 73 motorbikes and several cars were destroyed in the blast, which occurred the day before Pakistan celebrates Eid al-Fitr, the Muslim holiday at the end of Ramadan.
“It is a horrible tragedy,” said Makhdoom Syed Hassan Gillani, the parliamentary representative of Ahmedpur East, the small city in Punjab Province where the disaster occurred. “You can blame poverty 100 percent,” he added with a heavy voice. “It was poverty. It was greed. It was ignorance.”
Fuel is a high-value commodity in Pakistan, so even for those aware of the risks, the prospect of obtaining it free was too powerful a lure to ignore. Ahmedpur East has long suffered from poverty, illiteracy and a lack of modern facilities, and local residents have blamed the provincial government for spending money on urban areas at the expense of rural regions.
“People brought bottles, pots, buckets and other home utensils,” Mr. Gillani said. “Many people made several rounds and urged others to do the same.” He said people had planned to use the fuel for themselves and also to sell.
The devastation swept through several poor settlements near the crash site. “In one house, all eight men of the family died due to the fire,” Mr. Gillani said.
He denied reports that news of the spill had been broadcast over the loudspeaker of a local mosque, prompting many to go to the scene.
The authorities were investigating what had caused the driver to lose control, leading the tanker to overturn and creating the conditions for the inferno. One official suggested that a spark from a passing vehicle had probably caused the blast, but news reports quoted witnesses blaming a lit cigarette tossed by a passer-by.
The tanker had been traveling from the southern port city of Karachi to Lahore, the province’s capital. It was believed to be carrying 5,500 gallons of gas and high-octane fuel, officials and the state-run news media reported.
Muhammad Rizwan, a police official, said the police had “kept on telling people to leave the crash site, but people wouldn’t listen and more kept coming.”
“We knew it was dangerous,” he said, “and if there were more cars and bikes, the casualties would have been much higher.”
The injured were taken to the district hospital and Victoria Hospital in neighboring Bahawalpur, but the response was hindered by a shortage of facilities to treat burn victims.
The seriously injured were ferried to a hospital in Multan, about 80 miles to the north, which has a burn treatment unit. The Pakistan Army said it had sent two helicopters to help with the rescue efforts.
Abdul Rashid, 30, one of those injured, said he and a friend had joined in collecting the spilled fuel after passing by the area and seeing others trying to scoop it up from the overturned tanker.
“I parked my bike by the road and waited while my friend went to collect the fuel,” said Mr. Rashid, who had burns on one hand and a leg. “We did not have any bottles, so we asked people and got one. The bottle was small, so my friend went thrice to collect the fuel.”
He said he did know what had happened to his friend after the fire broke out.
Mr. Gillani said that even though the word danger was clearly written at the rear of such tanker, people did not take heed. “Many were not even aware of the risk they were putting themselves into,” he said.
There was no immediate information about what had caused the tanker to overturn: speeding at a sharp turn, a burst tire or something else.
Muhammad Shehbaz Sharif, the chief minister of Punjab, expressed his grief over the loss of life, said an aide, Salman Sufi.
“The chief minister is monitoring the situation and has directed the authorities to provide the best medical facilities to the injured,” Mr. Sufi said.
He said the fire had probably been started by an engine spark that caused the fuel tanker to explode, though he noted that the exact cause was being investigated.
Mr. Sufi said the driver of the tanker had avoided serious injury because the crash had taken place “long before” the explosion, and a provincial government spokesman said the driver had been taken into custody, Reuters reported.
Prime Minister Nawaz Sharif, who was in London on a private visit, cut short his stay and was returning to Pakistan, officials said. Imran Khan, the country’s most prominent opposition politician, called the accident “a national tragedy of epic proportions.”
Many of the dead were burned beyond recognition, said Dr. Mohammad Baqar, a senior rescue official in the area. They will have to be identified through DNA.
Abdul Malik, a local police officer who was among the first to arrive, said he had “never seen anything like it in my life,” The Associated Press reported. “Victims trapped in the fireball. They were screaming for help.”
When the fire subsided, he said, “we saw bodies everywhere, so many were just skeletons.”
An earlier version of this article misspelled the surname of the parliamentary representative of Ahmedpur East. He is Makhdoom Syed Hassan Gillani, not Gilani.