MEXICO CITY, Dec. 20 (Xinhua) -- A pipeline explosion in Puebla state could either have been caused by a duct problem or fuel theft, a Petroleos Mexicanos (Pemex) official said Monday.
The explosion took place in the early morning on Sunday, killing 28 and injuring 52, including 5 in serious condition. Eighty homes were also destroyed.
Juan Jose Suarez Coppel, chief executive officer of state-run Pemex, said the precise cause of the explosion cannot be determined until the National Attorney General's Office and technicians from the Mexican Petroleum Institute finish their investigation.
However, the official said there was a trench at the site of the explosion, which could mean there was a hidden valve there.
Suarez Coppel also said the duct which runs from Puerto de Coatzacoalcos to Venta de Carpio was repaired in 2008, including various sections in the region that go to San Martin Texmelucan in Puebla state, where the explosion took place.
He also said Pemex found the fuel leak almost immediately, due to abnormal pressure levels in the duct.
Suarez Coppel said there are some criminal groups that extract hydrocarbons using sophisticated technology that prevents officials from noticing the theft. The theft is usually carried out by people who work at the agency who have inside knowledge of the ducts.
Some 5,000 people were affected by the explosion, and Pemex has offered institutional support for them.
This year alone, Pemex has detected at least 380 hidden valves, including 100 in this duct and 60 in the pipeline that goes from San Martin Texmelucan to Venta de Carpio, in the state of Mexico.