CARACAS, Venezuela (AFP) — A 2012 explosion that killed 42 people at an oil refinery in Venezuela was “sabotage,” President Nicolas Maduro said Saturday, accusing opponents of being responsible.

Maduro cited an international investigation as finding that the incident was the product of “sabotage by desperate actors who believed that a refinery fire would help them win the elections against (late president Hugo) Chavez”.

Venezuela is South America’s biggest oil producer and firefighters struggled for days to put out the blaze triggered on August 25, 2012 at the Amuay refinery, which produces 645,000 barrels per day at normal capacity. Dozens were also injured in the blast.

The incident was initially blamed on a gas leak said to have caused the fire and explosion of nine fuel tanks. The blast tore through homes, businesses and part of the refinery.

Maduro claims the Opposition used the incident to try to chip away at Chavez’s popularity. But the late president won the October 2012 elections before dying of cancer on March 5.

In June, Maduro had accused the Opposition of being behind the blast on the basis of the attorney general’s probe, but this was the first time he cited an international investigation.

The president did not indicate who conducted the latest probe.

There have been similar incidents at refineries in oil-rich Venezuela in recent months, some of which have also been blamed on sabotage.

Venezuela has the largest oil reserves in the world, with the Government estimating that at 297.57 billion barrels its reserves surpass those of Saudi Arabia, which has the world’s biggest refining capacity.

Venezuela is also the fifth largest exporter of oil.