Some 2,500 rescue workers - aided by specially trained dogs - continued to pore through rubble Saturday at the Mexico City headquarters of state-owned oil monopoly Petroleos Mexicanos, where an explosion two days ago left 33 dead and more than 100 injured.

"The rescue efforts are continuing throughout the affected area. Personnel with the Government Secretariat, the emergency management office, the army, the navy, Cenapred (the federal disaster prevention agency), and of course Pemex, are there," a spokesperson for the oil company told reporters.

Pemex CEO Emilio Lozoya visited the office complex Saturday to supervise the work of the rescue teams and later attended several wakes to offer his condolences to family members of workers who died in the explosion.

Pemex on Saturday published the names of 32 of the 33 fatalities on its Web site, the company spokesperson said, adding that one woman who died in the blast has not yet been identified.

The explosion occurred in the basement of one of the complex's buildings. The cause has not yet been determined and, according to official reports, investigators have not found indications of a fire, smoke nor an odor of flammable substances.

The main tower of the office complex, a 56-story structure, was not damaged in the blast.

President Enrique Peña Nieto declared three days of national mourning in the wake of the tragedy. EFE