Mexico: Fatal oil HQ blast blamed on gas leak

The explosion that ripped through the headquarters of Mexico's state oil monopoly last week, killing at least 37 people and injuring more than 120, has been blamed on a gas leak.

The blast occurred at the Pemex office complex in Mexico City on Thursday, prompting speculation that it may have been a deliberate act of sabotage. But officials said on Monday that no trace of explosives had been found.

The Attorney General, Jesus Murillo, said the explosion was caused by an accumulation of gas, thought to be methane, in the building's basement.