One person remains unaccounted for amid the rubble at the Pemex compound in Mexico City. The blast injured 121 others and 35 people remain hospitalized, eight in critical condition, MNI said Monday.
Speculation abounds about the cause and nature of Thursday's blast though analysts said it is "likely" an accident of some sort.
It happened in the basement of an administrative building and was strong enough to blow out windows in the neighboring 52-story skyscraper.
That has put pressure on newly elected President Enrique Pena Nieto to produce a report that satisfies the public.
Mexico Attorney General Jesus Murillo Karam pledged Friday afternoon the government's commitment to transparency in investigating the blast.
"The government of Mexico is prepared to discover the truth," he said. "Be it accident, carelessness or attack."
The explosion is one of the worst for the energy sector in Mexico's history. A 2007 fire at a gas distribution center near the U.S. border left at least 30 people dead.
Alejandra Leon, an analyst for IHS CERA, told Bloomberg News from Mexico City the Pemex incident last week was likely an accident.
"At this point, I don't think it will have any impact" on the energy sector, she said. "Especially if this is just an accident, which is the most likely cause."