Rescue workers pulled more bodies from debris at the headquarters of oil giant Pemex on Friday after a powerful explosion killed at least 33 people and threw a spotlight onto the state-run company's poor safety record.
Scenes of confusion and chaos outside the downtown tower block in Mexico City have dealt another blow to Pemex's image, just as Mexico's new President is seeking to court outside investment for the 75-year-old monopoly.
Thursday's blast occurred at a Pemex building next to the 50-storey skyscraper. A further 121 were injured, the company's chief executive, Emilio Lozoya, said.
Officials have been unable to say how many people could still be trapped in the wreckage of the office block, which remains cordoned off. A military paramedic at the scene said there were likely many and expected the death toll to rise.
Mr. Lozoya said it was not clear what caused the midafternoon explosion, which has been the subject of speculation ranging from a bomb attack, to a gas leak, to a boiler blowing up.
Pemex, both a symbol of Mexican self-sufficiency and a byword for security glitches, oil theft and frequent accidents, has been hamstrung by inefficiency, union corruption and a series of safety failures costing hundreds of lives.
The latest Pemex disaster is also one of the first serious tests for President Enrique Pena Nieto, who took office in December saying overhauling the company was a top priority.
Investors have been closely following how far he will go in enticing private capital to boost flagging oil output in a country that is the world's No. 7 producer.
"This incident speaks very poorly of the image of Pemex management, and that's interpreted as additional risk in the market," said Miriam Grunstein, an energy researcher at Mexico's CIDE think tank.
Mexican officials have not ruled out sabotage.
The blast followed a September fire at a Pemex gas facility near the northern city of Reynosa that killed 30. More than 300 were killed when a Pemex natural-gas plant on the outskirts of Mexico City blew up in 1984.
Eight years later, about 200 people were killed and 1,500 injured after a series of underground gas explosions in Guadalajara, Mexico's second-biggest city. An official investigation found Pemex was partly to blame.
Whatever caused the explosion, the deaths and destruction will put the spotlight back on safety at Pemex, which only a couple of hours beforehand had issued a statement on Twitter saying it had managed to improve its record on accidents.
"I suspect this was a bomb," said David Shields, an independent oil analyst based in Mexico City. "There are clandestine armies across Mexico, not just the [drug] cartels."
Mr. Shields pointed to the bombing of Pemex pipelines in the eastern state of Veracruz in 2007. A Marxist rebel movement took credit for some of the blasts.
Meanwhile, George Baker, director of Energia.com, a Houston-based energy research centre, said past history suggested the government could seek to exploit the incident.
He pointed to the 1992 Guadalajara blast and the subsequent deal that followed to overhaul the Pemex administration led by then-president Carlos Salinas, like Mr. Pena Nieto a member of the Institutional Revolutionary Party, or PRI.
"Salinas said he wanted a response from Pemex, and months later Pemex announced a restructuring. The restructuring had nothing to do with the Guadalajara accident, but it was used as a pivot to do something," Mr. Baker said.
Mr. Pena Nieto has yet to reveal details of his Pemex reform plan, which already faces opposition from the left.
Both Mr. Pena Nieto and his finance minister were this week at pains to stress the company will not be privatized.