Fires raged at Venezuela's Amuay refinery after a predawn explosion rocked the facility on August 25 and left at least 42 dead, dozens wounded, and hundreds of homes demolished. The blast was the world's deadliest refinery accident in 15 years.

The catastrophe's exact causes haven't been determined, but Energy Minister Rafael Ramírez, president of the state's oil company Petróoleos de Venezuela SA (PDVSA), said on Venezuelan television that a gas leak had appeared in a fuel storage tank area and formed a cloud that burst into a ball of flame despite the efforts of workers. "All this happened very fast, and the explosion occurred almost immediately," Ramírez said.

(Related Story: "Isaac, Refinery Woes Drive Spike in U.S. Gas Prices")

"I don't think there is enough information about this incident at this point, but obviously I think all of the oil industry and the government agencies that have some responsibility for refinery safety are going to be very interested in finding out what happened and what lessons can be learned," said Don Holmstrom of the U.S. Chemical Safety Board, (CSB) the independent federal agency responsible for investigating all U.S. industrial chemical accidents.

—Brian Handwerk

This story is part of a special series that explores energy issues. For more, visit The Great Energy Challenge.

Venezuelan Refinery Under Scrutiny After Deadly Blaze

The fires are out at Venezuela's Amuay facility four days after the deadliest refinery accident in 15 years. But questions about exactly what happened, and why, are only beginning.