SHANA� -- The dense smoke and blaze seen above one of Tabriz Refinery�s units was caused by burning hydrocarbon gases after overhaul of the refinery, an official with the refinery said.

Speaking to IRNA on Tuesday, Head of public relations and international relations at Tabriz Refinery Shaker Khafaei said that overhaul of the facility was complete without any incidents and the units were being prepared for resumption of their operation.

�When relaunching the units, in order to observe safety measures, we had to shutter one of the units which caused accumulation of a mass of hydrocarbons at a relatively short period of time in the safety flare of the refinery causing the smoke and flames,� he said.

On Tuesday, images were publishes on social media showing dense smoke and fire above the refinery.