Venezuela’s largest oil refinery went up in flames Saturday, leaving 26 dead and some 80 people wounded, officials said.

Among the dead was a 10-year-old boy and 17 members of the National Guard, who are stationed at a post at the Amuay complex.

The refinery is one of the biggest in the world, producing 645,000 barrels of oil per day.

Energy Minister Rafael Ramirez, president of the state-owned Petroleos de Venezuela oil company that runs the refinery complex said the blast occurred at 1:15 a.m.  At least two storage tanks were ignited, and other facilities at the refinery were damaged as well. A number of homes opposite the complex were also damaged.

Ramirez, who appeared on national television, said the explosion was caused by a gas leak and was an accident. President Hugo Chavez, who called it “sad and painful,” declared a 3-day national mourning period.

The Amuay oil refinery is located in Punto Fijo in Falcon State, in the Peninsula of Paraguana. The conflagration is the OPEC nation’s worst industrial accident in recent memory.

Venezuela is South America’s largest oil producer – but it also has a strong connection with Iran, a fellow member of OPEC, as well.

In May of this year, the National Iranian Oil Company and Petroleos de Venezuela signed a $2 billion contract to develop the dobokubi oil field in Venezuela’s Orinoco Oil Belt together. The oil field’s capacity is expected to increase from 14,000 barrels to 40,000 barrels a day in the first phase of development.