33 people are now confirmed dead after a blast Thursday afternoon at the headquarters of the Pemex oil building in Mexico City, and officials say, that number will go up.

As rescue workers sift through mangled debris, more and more victims are pulled from the rubble.

More than 120 people were injured in the incident... Mexican President Enrique Pena Nieto visited some of the victims earlier on Friday.

Officials are now turning their attention to the cause of the explosion, of which there is much speculation-- from bomb attack, to gas leak to a boiler blowing up.

One thing that is certain, the state run oil company has been blighted by corruption, inefficiency and frequent accidents.