A fire tore through part of Russia's Novoshakhtinsk refinery on Wednesday just 8 kilometres from the border with Ukraine after drones were spotted flying over the oil plant.
Social media footage showed a drone flying towards the refinery before a large ball of flame and black smoke bellowed up into the summer sky.
TASS citied an unidentified source in the local authorities as saying that one of the drones had crashed into a heat transfer unit at the refinery.
Reuters was unable to independently verify the reports or the videos on social media. The plant's spokespersons could not be reached for immediate comment.
The local emergency service said the blaze has been put out, Interfax news agency reported.
No one was injured at the refinery which has an annual capacity of up to 7.5 million tonnes, the emergency service said.
The plant is one of a few built in Russia in the past decades. It started operations in 2009.
Russia was investigating the cause of a large fire that erupted in at an oil storage facility in the city of Bryansk 154 km (96 miles) northeast of the border with Ukraine in late April.