PUNTO FIJO, Venezuela - Venezuela's biggest oil refinery remained shut down Tuesday after firefighters extinguished a blaze that raged for more than three days following an explosion that killed at least 41 people.

While fuel tanks smoldered at the Amuay refinery, Oil Minister Rafael Ramirez said officials expected to restart operations at the refinery in two days.

The blast early Saturday was the deadliest disaster ever at a Venezuelan refinery and has thrown open a national debate about safety and maintenance within the country's oil industry. The debate has also touched the presidential campaign, with President Hugo Chavez's rival calling for a transparent and thorough investigation.

The fire took longer to put out than officials had initially hoped. Ramirez had said Saturday that the state oil company would be able to restart the refinery "in a maximum of two days," then later said it would be two days once the fire was out.

"Now of course come all of the subsequent tasks: evaluation, securing the entire area," Ramirez told the Caracas-based television network Telesur on Tuesday morning. He said firefighters were still working in the area spraying the tanks with foam to cool them down.

"We need to check all the lines, all the connections, all the valves," Ramirez said. He added that the disaster hadn't affected the refinery complex's productive capacity, although operations were halted while the fires burned.

Officials said the explosion killed at least 41 people, including at least 20 National Guard soldiers stationed next to the refinery, and injured more than 150.

Government officials had said on Monday that the fire was under control but then announced that a third tank had begun burning. Residents said the flames finally began to diminish several hours before dawn on Tuesday.

Criticisms of the government's response came from some of the refinery's neighbors as well as oil experts.

Officials have said a gas leak led to the blast, but investigators have yet to determine the precise causes.

Investigators entered damaged areas to gather clues, Ramirez said. He declined to discuss details of the probe but said officials had followed safety protocols once they detected the gas leak in an area of fuel storage tanks shortly before the blast.

Another state oil company official told Chavez during a televised conversation Sunday that at about midnight officials had detected the leak and "went out to the street to block traffic."

Residents said they had no official warning before the explosion hit at about 1 a.m. Saturday. The blast knocked down walls, shattered windows and left streets littered with rubble.

On Tuesday, residents said they were relieved the fire was out.

Edgar Medina was working with his father to clear rubble that blocked the way to what remained of their windowless home. "Now what we hope is that they help us rebuild everything."

Chavez, who visited injured victims in a hospital Monday, announced the creation of a 100 million bolivar ($23 million) fund to help rebuild. He said more than 500 homes were damaged.

On Tuesday, Chavez spoke at a televised Cabinet meeting and praised state oil company officials and firefighters for their handling of the disaster. He paused for a live appearance by Gov. Stella Lugo in Falcon state, where the refinery is located, as she presented homes to families at a new government housing project.

The disaster occurred little more than a month before Venezuela's Oct. 7 presidential election. Opposition candidate Henrique Capriles said Monday that the tragedy shouldn't be politicized, but he also strongly criticized a remark by Chavez, who said that "the show should continue, with our pain, with our sorrow, with our victims."

"It seems irresponsible, insensitive ... to say 'the show should continue,"' Capriles told reporters. He repeated past criticisms about the number of accidents at the state-owned oil company and said the government "has to give answers."

The refinery is among the world's largest and is part of the Paraguana Refining Center, which also includes the adjacent Cardon refinery.

More debate about the government's response is likely during the presidential campaign.

Some Chavez critics and oil industry experts say insufficient maintenance could have made such a disaster likelier. Chavez and other government officials deny that, saying billions of dollars have been spent in recent years on upkeep at refineries including Amuay.

Chavez's government has been hit recently by other infrastructure-related problems including a prison riot that killed 25 last week, the collapse of a major highway bridge and power outages in parts of the country.

Pollster Saul Cabrera's said he doesn't think the refinery disaster is likely to cause significant political damage for Chavez nor shifts in most Venezuelans' views about the government.

Cabrera said that like in the case of the collapsed bridge, the apparent problem behind the refinery explosion "is government inefficiency, but it seems that doesn't matter much to people."

"It doesn't affect (Chavez) among his voters, which are nearly half the country," Cabrera said.

Still, Cabrera predicted the vote will result in a very tight race and predicted those who are undecided "are going to end up deciding the election."

His polling firm, Consultores 21, found in a survey earlier this month that the two candidates were nearly even, with Capriles at nearly 48 percent and Chavez garnering about 46 percent. The poll consulted 1,000 people and had an error margin of about 3 percentage points.

Other polls have given a significant lead to Chavez. The Venezuelan polling firm Datanalisis found Chavez with a 15-point lead in one June poll, but also said 23 percent of those surveyed were undecided or didn't reveal a preference.

The refinery fire appeared to contribute to fluctuations in U.S. gasoline futures, though Hurricane Isaac's approach toward the U.S. Gulf Coast appeared to have a bigger effect.

Gasoline futures rose 7.7 cents, or 2.5 percent, to $3.155 on Monday in New York, on concerns about supply disruptions from the storm and, to a degree, the closed Venezuelan refinery. On Tuesday, U.S. gasoline futures fell 2.87 cents to $3.126 as traders waited to see how big an impact Isaac has on U.S. refineries, and as Venezuelan officials said the Amuay refinery would restart in two days.

Associated Press writers Fabiola Sanchez and Ian James in Caracas and AP Business Writer Sandy Shore in Denver contributed to this report.