At least 21 people were killed and over 71 people were injured in a massive fire that broke out at the site of an illegal fuel tap in central Mexico on Friday.
Governor of Hidalgo state Omar Fayad said that the explosion took place in Tlahuelilpan, about 105 kilometres north of the Mexico city.
"What we know is that it was an illegal fuel theft site, and that authorities were aware of it" when it burned, Fayed added.
Hours later, and after sundown, the first images of the tragedy were shown on television, with desperate people fleeing the scene, screaming for help.
Federal and state firefighters and ambulances run by state oil giant Pemex were headed to the area to help burns victims, the governor added, as victims were ferried off to hospitals.
"I am deeply saddened by the grave situation suffered by Tlahuelilpan because of the explosion of a pipeline," President Andres Manuel Lopez Obrador wrote on Twitter.
The tragedy comes as anti-corruption crusader Lopez Obrador presses implementation of his national fuel theft prevention plan.
Illegal taps of Pemex pipelines cost Mexico an estimated $3 billion in 2017.
The government has shut off key pipelines until they can be fully secured and deployed the army to guard Pemex production facilities.
But the strategy to fight the problem has led to severe gasoline and diesel shortages across much of the country, including Mexico City, forcing people to queue for hours -- sometimes days -- to fill up their vehicles.
The president, who took office on December 1, has vowed to keep up the fight and asked Mexicans to be patient.
Meanwhile, authorities have opened 1,700 individual investigations for fuel theft, which became a massive black-market industry in Mexico under previous governments, involving powerful drug cartels and corrupt Pemex insiders.
Tanker trucks are being used to deliver fuel, but experts say there are not nearly enough of them.
Mexico City residents faced a second week of fuel shortages, though lines at service stations appeared shorter than the previous week.
Lopez Obrador called on private companies to step up gasoline imports, suggesting they bore some of the blame for the shortages.
The roots of the fuel theft problem run deep in Mexico, where the practice -- known locally as "huachicoleo," or moonshining -- is big business for some communities.
(With agency inputs)