A blaze at the Novoshakhtinsk oil refinery in Russia’s Rostov region has been burning for four consecutive days following a Ukrainian drone attack, regional officials confirmed Sunday.

The facility, which has an annual processing capacity of around 5 million metric tons of crude — or roughly 100,000 barrels a day — was first hit on Thursday. The plant primarily produces fuel for export.

Authorities reported that more than 400 personnel and about 150 units of equipment, including specialized firefighting trains, are currently engaged in the operation.