Mexico probes if blast was attack or accident, 33 dead

Mexico's government vowed to find out whether an explosion that killed 33 people at the headquarters of its state-run oil monopoly Pemex was a deliberate attack or yet another stain on the company's poor safety record.

Rescue workers continued to pull bodies from the debris on Friday and officials said the search would continue until they account for everyone inside the Mexico City building.

Government officials have refused to speculate over what caused the explosion on Thursday but said they had deployed large teams of experts to pore through the wreckage.

"The government is determined to find out the truth, whatever that may be ... whether it was an accident, negligence or an attack, whatever," Attorney General Jesus Murillo said on Friday evening. "We are not going to rule out anything."

He said the explosion did not cause a fire but refused to be drawn on what that implied about the cause. Parts of the reinforced concrete ground floor of the building caved in, and the ceiling was a mess of twisted metal pipes and ducts.

The blast at Pemex's complex in the capital killed at least 33 people and a further 121 were injured. The scenes of chaos have dealt another blow to Pemex's image, just as Mexico's new government is seeking to open up the oil industry to more private investment.

Speculation over the cause has ranged from a bomb attack, to a gas leak, to a boiler blowing up.

"A fatal incident like yesterday's cannot be explained in two hours. We are working with the best teams in Mexico and from overseas. We will not speculate," Pemex's chief executive, Emilio Lozoya, said on Friday.