Iran’s largest oil refinery, in Abadan, was rocked by an explosion just as Mahmoud Ahmadinejad was visiting.

Iranian media reports that the explosion caused a large fire in one section of the refinery that sent thick black smoke pluming into air.

Ahmadinejad is in the southwestern city of Abadan to inaugurate the expansion of the refinery’s output to 400,000 barrels per day.

Conflicting reports have been published regarding injuries. While some have said more than 20 people were injured in the explosion, others say two dead and 12 wounded.

The Abadan refinery chief announced that the explosion was caused by a leak and technical difficulties, but workers had it under control within ten minutes.

Mehr news agency first reported that a test led to the explosion but later it claimed that a leak in one of the pipes caused the explosion and poisoned some workers with gas.

Mehr reports that even though the fires have been extinguished, a heavy black cloud of smoke hangs over the refinery.

It adds that Islamic Republic security forces are examining the cause of the explosion.

The report seems to suggest the cause is not yet fully clear, and further explosions may be possible.

Mehr adds that while the fires have been extinguished, poisonous gas is still being released into air.

Ahmadinejad has reportedly ordered the injured and poisoned workers to be airlifted to Tehran for treatment. Iran’s is the world’s fourth largest producer of crude oil but it does not have sufficient refinery capacity to meet its domestic demands. Therefore, it has been trying to boost refinery capacity to offset the fuel shortage.