I would think sabotage before I thought of a wayward cigarette.
I doubt a cigarette, but decades of working in the oil/gas industry has taught me fires are far too common. Spread of fire to this extent is more rare, but then, this is Pemex and has a rather bad history for safety.
Several deadly accidents have occurred at Pemex facilities in recent years. In September 2012, a leak at a Pemex pipeline near the U.S. border exploded, killing 29 and injuring 46. In 2013, 32 people died and 121 were injured in a gas explosion at Pemex headquarters in Mexico City.
http://fuelfix.com/blog/2015/04/01/pemex-platform-fire-kills-one-worker-injures-45/
Also I’m sure this did not help the operations and maintenance budgets after the decline in oil prices for Pemex.
Pemex bondholders are growing concerned over the companys financial health after the Mexican government took $3.4 billion from the state owned explorer and producer late last month.
The Finance Ministry said it withdrew the funds on December 26 to make management of public-sector finances more efficient as the country braces itself for production declines and low oil prices.
Mexico.