Explosion rocks headquarters of Mexican oil giant Pemex

The headquarters of state-owned Pemex are pictured on April 14, 2009 in Mexico City (AFP/File, Omar Torres)

MEXICO CITY (Reuters) - An explosion rocked the ground floor of the Mexico City headquarters of Mexican state oil monopoly Pemex on Thursday, causing injuries and damage to the building.

Pemex said the building had been evacuated but did not say what caused the explosion. Before announcing there had been a blast, the company said the building had suffered a problem with its electricity supply.

Mexican television images showed debris scattered near the base of the skyscraper and injured people being taken out on stretchers.

Local media reported that 22 people had been injured in the explosion and that one person had died in the building.

Plaster had fallen from the ceiling of the basement, and the situation at the Pemex tower was "delicate," a spokesman for local emergency services said.

(Reporting by Gabriel Stargardter; Editing by Doina Chiacu and Sandra Maler)