At least eight workers died after fire broke out in an oil sludge-processing firm on Saturday in the West Siberian region of Khanty-Mansiisk, the hinterland of Russian crude production, the Emergencies Ministry said. The fire at a sludge storage has been put out, the ministry said in a statement. The Investigation Committee said the cause of fire could be an explosion, while the state-owned RIA Novosti news agency said, citing a law-enforcement source, the plant caught fire after gas exploded.