By Agence France-Presse

Mexico has opened an investigation into what caused a deadly pipeline explosion, including possible negligence by authorities, the attorney general said Monday, as the death toll rose to 91 people.

It is still unclear exactly how events unfolded leading up to the Friday blast, which occurred as hundreds of people rushed to collect fuel in buckets and jerrycans from a geyser of gasoline that was spouting from an illegal pipeline tap near the town of Tlahuelilpan, in the central state of Hidalgo.

The death toll from the blast and ensuing fire has now risen to 91 people after two more victims died in hospital, Governor Omar Fayad told Mexican radio network Formula.

“Unfortunately, we have 52 wounded, the vast majority of whom are in very serious condition, with a very bad outlook,” he said.

Attorney General Alejandro Gertz said investigators were trying to determine who tapped the pipeline — whether locals acting alone or one of the criminal gangs that have turned fuel theft into a booming industry in Mexico.

Possible negligence by the authorities responsible for the pipeline is also “a fundamental issue” in the investigation, Gertz told a press conference.

“The timeline of events has to be made absolutely clear and precise. To do that, we’re going to talk to each and every authority who intervened,” he said.

The interrogation will include officials from the defense ministry, the police, state oil company Pemex and the Hidalgo state government and prosecutor’s office.

Video taken before the explosion shows how some 700 people gathered at the pipeline as it sent a jet of gasoline into the air, while army soldiers stood by, apparently doing little to intervene.

The almost festive scene turned into a horror show after the explosion, as screaming victims in flaming clothes fled the enormous fire, some with severe burns.

Nearly four hours elapsed between the moment the leak was detected and the moment the pipeline was turned off, according to the government.

Gertz said investigators were also examining whether the recent murders of three ringleaders of Hidalgo fuel-theft gangs could have been a factor.

Authorities say it could take weeks to identify all the victims of the explosion, many of whom were burned beyond recognition.

The disaster occurred as President Andres Manuel Lopez Obrador’s government wages a massive crackdown on fuel theft, which cost Mexico an estimated $3 billion in 2017.