An explosion in the headquarters of Petroleos Mexicanos (Pemex) in Mexico City on Thursday left 14 people dead and 80 others injured, the Mexican oil giant said on its Twitter account.

An injured man receives treatment after an explosion in Mexico City, capital of Mexico, on Jan. 31, 2013. A powerful blast ripped through the landmark headquarters of Mexico's oil giant PEMEX in Mexico City on Thursday, killing one person, injuring more than 30 others and causing extensive damage to the building, according to local press.

Mexican Interior Minister Miguel Angel Osorio Chong also confirmed the death toll, saying the exact cause of the accident is still unknown.

The injured were taken to hospitals after the blast occurred around 3:55 p.m. (2155 GMT) in the administration building of B2 Pemex Tower, located in the downtown of Mexico City.

Pemex said that about 3,500 people were evacuated from the damaged building.

Emergency workers have been deployed to the site to search for people who may be trapped in the building. The Mexican Army also joined the rescue.

Three helicopters arrived to the scene to transfer those seriously wounded, while the building and its surrounding area have been cordoned off.

Pemex spokesman Francisco Montano confirmed earlier that there were "significant damages and injuries" in the blast, which reportedly occurred in an electrical substation that would have caused a collapse in the basement of the building.

The Pemex headquarter building is considered one of the highest in Mexico City, with a height of 211 meters and 54 floors.

Built in 1979, Pemex Tower is among the world's strongest skyscraper and one of the most seismic tolerance worldwide.

There are about 7,000 people working inside the building.

Source: Xinhuanet