Guardian: A deadly blast that killed at least 37 people at Mexican state oil monopoly Pemex's headquarters in Mexico City was caused by a build-up of gas, the government has said on Monday.
The attorney general, Jesus Murillo, said no trace of explosives was found at the site of the disaster, the latest in a string of safety lapses to hit the oil monopoly. President Enrique Pena Nieto is seeking to push through a major overhaul of Pemex.
"We have been able to determine that the explosion was caused by...