A major fire that tore through an oil refinery in the Iranian capital had been brought under control on Thursday, but was still not completely extinguished. "The fire at the refinery has been brought under control and will be completely extinguished by noon," the official IRNA news agency said, citing Shaker Khafai, spokesman for Tehran Oil Refining Company. A column of black smoke was still visible over the site of the inferno around midday, AFP journalists reported, although it was not as thick as the day before. Teams of firefighters were seen battling the blaze in footage from the scene broadcast by state television. The authorities say the blaze broke out at 7.30 pm (1500 GMT) on Wednesday after an explosion caused by a leaking gas pipe, resulting in a huge fire. An investigation is underway, according to AFP. The refinery is located in a large industrial zone on Tehrans outskirts, only a few hundred metres (yards) from residential areas. It has been in operation since 1968 and has a capacity of 250,000 barrels per day, according to IRNA. Industrial accidents are common in Iran. On May 23, nine people were injured in a blast at a plant producing explosive materials in central Iran, local media reported, while three days later, a pipeline explosion at a petrochemical complex near Irans Gulf coast left one dead. Meanwhile, Iran views arch-rival Israel as the top suspect behind two incidents in the past year at its nuclear sites that Tehran has branded acts of sabotage. Some in the Islamic republic see the various events as the result of attacks by Israels security forces, while others consider US sanctions -- which almost completely isolate Iran from the rest of the world, complicating the maintenance of industrial facilities -- as a more likely cause.