Fuel storage tanks burning at a refinery in Venezuela
Venezuelan Vice-President Elias Jaua says a fire at the country's biggest oil refinery has spread.
He said a third tank was ablaze following Saturday's explosion, which is now known to have killed 48 people.
The opposition candidate in the forthcoming presidential election, Henrique Capriles, said government inefficiency under President Hugo Chavez was to blame, reports the BBC.
The president has ordered an urgent investigation into the blast.
"When things aren't done properly, with responsibility, then you have to prepare for the consequences," Capriles said.
Capriles and other critics of Chavez' government have said under-investment by state oil company PDVSA has led to a decline in production and safety standards.
But Chavez said there was no evidence the blast was the result of poor maintenance.
He said firefighters had the blaze under control, despite its spread to a third tank.
Stella Lugo, the governor of Falcon state, where the refinery is located, said on Monday that the number of confirmed dead had risen from 41 to 48.
She said about half of those who had died were members of the National Guard who had been protecting the refinery.
Ms Lugo said 31 people remained in hospital.
Government officials said the blast occurred at 01:15 local time on Saturday when a gas leak created a cloud that ignited.
More than 200 homes and 11 businesses were damaged.
Venezuela has the world's biggest certified oil reserves.