(Reuters) -A fire that broke out on Monday at the Ufimsky oil refinery, one of Russia's largest, was due to technical issues and has been extinguished, Russia's emergency ministry said, adding that the refinery had continued operations.

It wasn't clear if output was stopped at any point because of the blaze. Bashneft's press service told Interfax that the fire did not affect the main production facilities.

The Bashneft-owned refinery, about 1,500 km (932 miles) east of the border with Ukraine, has capacity of 168,000 barrels per day, LSEG data shows, and its oil supply comes mainly from surrounding Bashkiria and western Siberia.

"The fire is related to technical issues," and broke out near a furnace, the region's emergency ministry said on the Telegram messaging app, citing initial findings.

Bashkortostan's leader, Radiy Khabirov, said no traces of drones were found, according to Interfax news agency, and that production was continuing as normal, he said.

A video posted on social media and verified by Reuters showed that an oil refinery in Ufa, the largest city in Bashkortostan, was on fire. It was not possible to immediately verify the date of the footage.

Earlier, the emergency ministry said no harmful substances exceeding unsafe levels were recorded in the air near the refinery.

About 100 firefighters helped battle the fire, which was finally put out at about 8 a.m. (0500 GMT) Interfax said.

Several Russian channels on Telegram, including the SHOT Telegram, said the fire followed an explosion at the refinery, but Reuters could not independently verify the reports.

There were no overnight reports of a drone attack on Bashkiria, sandwiched between the Volga river and the Ural mountains.

There was no immediate comment from Ukraine. Its forces have systematically targeted Russian energy infrastructure to try to disrupt Russia's economy and ability to fund the war in Ukraine.

(Reporting by Lidia Kelly in Melbourne; Editing by Clarence Fernandez and Bernadette Baum)