Rescue teams work tirelessly at the site of a deadly blast at Mexican oil giant Pemex's headquarters in Mexico City.
37 people died in the explosion, with over 120 others injured.
Mexican authorities have concluded that the blast was caused by a build-up of gas in the building.
No explosives were found at the site.
(SOUNDBITE)(Spanish) ATTORNEY GENERAL JESUS MURILLO KARAM, SAYING:
"This explosion caused a structural collapse. The collapse is what caused the greatest number of deaths, as I said originally. These are preliminary results that allow us to identify the cause. Without a doubt, there is still much to do to be able to identify the gas that caused the explosion, the exact point of origin, and the analysis of possible responsibility if it exists."
The blast had prompted speculation that the incident could have been an act of sabotage.
But the deadly explosion, the latest in a string of safety lapses to hit the oil giant, has sparked renewed criticism of the company's poor safety record.
