Venezuela has ordered a thorough probe into the Amuay oil refinery explosion, which left at least 39 people dead and more than 80 injured.
Announcing the probe, President Hugo Chavez declared three days of national mourning. He said the tragedy has touched everyone in the country.
In an unusual step, Chavez telephoned state TV to say: "This affects all of us. It's very sad, very painful."
"I want to send out to the families of those who died, civilians and military, all our pain, mine, that of all my family, everyone in the national government and the people of Venezuela," he said.
Of the dead, 18 were members of the National Guard stationed at the refinery and 15 were civilians. Six bodies are yet to be identified, according to Vice President Elias Jaua, who travelled to the site of the explosion, one of the worst in the country's recent history.
Several homes and establishments around the refinery were also affected by the blast. Fire officials said the blaze was under control and ruled out any possibility of further explosions.
Energy Minister Rafael Ramirez told state TV that the blast was sparked by a gas leak. The reason for the gas leak is yet to be ascertained.
Venezuela is one of the largest oil producers and exporters in the world. The country has proven reserves of 297 billion barrels, more than the Arab countries' 265 billion barrels, Chavez claimed in 2011.
The Paraguaná Refinery Complex, which houses the Amuay refinery, the Bajo Grande refinery and the Cardón refinery, is the second largest refinery complex in the world, after the Jamnagar refinery in India.
The complex handles more than 70 per cent of Venezuela's refining capacity and is owned by the state-owned company Petróleos de Venezuela.