Russia’s NORSI refinery, the country’s fourth-largest oil refinery and second-largest gasoline producer, suspended crude oil processing on Wednesday following a Ukrainian drone attack, according to three industry sources.

Nizhny Novgorod Region Governor Gleb Nikitin said an unspecified industrial facility was damaged in a Ukrainian drone attack on the region on August 26, The Caspian Post reports, citing Reuters.

Lukoil, which owns NORSI, did not immediately respond to a request for comment.

The sources said the attack damaged several processing units, inter-unit infrastructure and other plant facilities. They could not estimate how long repairs would take or when crude processing would resume.

All of Lukoil’s major Russian refineries are currently offline. Its Perm refinery stopped operations following a drone attack on August 21, while the Volgograd refinery suspended processing on July 31.

NORSI has an annual crude processing capacity of about 15 million metric tons. It can produce approximately 5 million tons of gasoline, more than 5 million tons of diesel, 2 million tons of fuel oil and around 500,000 tons of bitumen.