CARACAS, Venezuela (AP) -- A huge explosion rocked Venezuela's biggest oil refinery and unleashed a ferocious fire on Saturday, killing at least 26 people and injuring more than 80 others in one of the deadliest disasters ever to hit the country's key oil industry.
Balls of fire rose over the Amuay refinery, among the largest in the world, in video posted on the Internet by people who were nearby at the time. Government officials pledged to restart the refinery within two days and said the country has plenty of fuel supplies on hand to meet its domestic needs as well as its export commitments.
At least 86 people were injured, nine of them seriously, Health Minister Eugenia Sader said at a hospital where the wounded were taken. She said 77 people suffered light injuries and were released.
Officials said those killed included a 10-year-old boy, and that 17 of the 26 victims were National Guard troops stationed at a post next to the refinery.
President Hugo Chavez declared three days of mourning.
"This affects all of us," Chavez said by phone on state television. "It's very sad, very painful."
Chavez said he ordered a "deep investigation" to determine what caused the explosion.
Vice President Elias Jaua, who traveled to the area in western Venezuela, said the authorities tried "to save the greatest number of lives."
Officials said firefighters had controlled the flames at the refinery on the Paraguana Peninsula, where clouds of dark smoke still billowed in the afternoon.
The blast occurred about 1:15 a.m. when a gas leak created a cloud that ignited, Oil Minister Rafael Ramirez said. He said an adjacent National Guard post was severely damaged by the blast, along with nearby homes.
"That gas generated a cloud that later exploded and has caused fires in at least two tanks of the refinery and surrounding areas," Ramirez said. "The blast wave was of a significant magnitude."
Images in the early hours after the explosion showed the flames casting an orange glow against the night sky. One photograph showed an injured man being wheeled away on a stretcher.
Some people in surrounding areas were evacuated or fled, officials said.
Ramirez said a panel of investigators was being formed to probe the cause of the gas leak. A prosecutor was appointed to lead the investigation and troops were deployed to the area.
The explosion hit an area of storage tanks in the refinery, and nine of the tanks were damaged, Ramirez said.
"All of the events happened very quickly," Ramirez said. "When we got here in the middle of the night, at 3 or 3:30 in the morning, the fire was at its peak."
He said supplies of fuel had been cut off to part of the refinery, and that the fire had been brought under control, though the flames continued to burn up fuel in some of the tanks. Firefighters, he said, were using foam to extinguish the flames in one of the remaining tanks.
"This regrettable and sad event is controlled, is under control," Ramirez said on television, while plumes of smoke continued to billow.
Amuay is part of the Paraguana Refinery Complex, which also includes the adjacent Cardon refinery. Together, the two refineries process about 900,000 barrels of crude per day and 200,000 barrels of gasoline. Venezuela is a major supplier of oil to the U.S. and a member of the Organization of Petroleum Exporting Countries.
Ramirez said the state oil company Petroleos de Venezuela SA should be able to "restart operations in a maximum of two days."
"We want to tell the country that we have sufficient inventories of fuel. We have 10 days of inventory of fuel," Ramirez said. He said the country's other refineries were operating at full capacity and would be able to "deal with any situation in our domestic market. ... In that sense, we won't have major effects."
An official of the state oil company, known as PDVSA, said the country also has enough supplies on hand to guarantee its international supply commitments. The official spoke on condition of anonymity because he wasn't authorized to speak publicly about the matter.
In terms of international oil markets, the disaster is not likely to cause much of a ripple, said Jason Schenker, an energy analyst and president of Austin, Texas-based Prestige Economics LLC. Noting that other refinery accidents and shutdowns regularly occur around the world, he said: "There's likely to be relatively limited impact on global crude or product pricing."
"The real tragedy," he said, "is that these events continue to happen, not just in Venezuela but everywhere. It is a dangerous business."
While the cause of Saturday's disaster remains unclear, some oil workers and critics of Chavez's government have recently pointed to increasing numbers of smaller accidents and spills as an indication of problems within the state-run company.
"This tragedy is probably the worst one the oil industry has had in many years. Accidents happen, of course, although the problem with PDVSA is the inordinate amount of accidents that have taken place during the last years," said Gustavo Coronel, an energy consultant and former executive of PDVSA. Considering that record overall, Coronel said, "we are not talking about bad luck but about lack of maintenance and inept management."
Ivan Freites, a labor leader and employee who has worked at the refinery for 29 years, said workers had repeatedly alerted PDVSA officials to problems that they feared could lead to an accident.
"It's the first time that we see something like this in Venezuela, and it's not a coincidence because we've been complaining about problems and risks, including fires, broken pipes and a lack of spare parts," Freites said in a telephone interview on Saturday from an area located a few miles (kilometers) from the refinery.
"We warned that something was going to happen, a catastrophic event," said Freites, secretary general of a 1,200-member union of oil and natural gas industry workers in Falcon state.
Deadly explosions at pipelines and refineries have taken a toll over the years in various countries, in some instances claiming hundreds of lives.
In one deadly incident in Venezuela in 1993, a natural gas pipeline exploded beneath a highway in Las Tejerias, engulfing a passenger bus and cars. Officials said 36 people were killed.
Opposition leader Henrique Capriles, who is challenging Chavez in the country's Oct. 7 presidential election, expressed condolences to the victims and their families.
"We Venezuelans are one, and we grow in the face of this type of situations," Capriles said.
Associated Press writers Jorge Rueda, Fabiola Sanchez and Christopher Toothaker contributed to this report.