Four workers were injured when southwest Iran's Abadan Refinery, the biggest in the country, caught fire Wednesday, the semi-official Fars news agency reported.

The fire broke out in the refinery's cracker unit which produces gasoline, said the report, quoting deputy chief of Iran's Parliament's Energy Commission, Abdollah Kabi.

Firefighters are trying to contain the fire and the cause of the accident would be clarified quickly, said Kabi.

In May, an explosion hit the cracker unit of Abadan Refinery when Iranian President Mahmoud Ahmadinejad attended an inauguration ceremony of the new gasoline producing project in the refinery.

Later reports said that four people were killed in the explosion and some 20 people were injured.

Head of the Iranian Parliament Energy Commission Hamid-Reza Katouzian said the blast in the oil refinery was caused by a technical failure.