An explosion occurred early in the morning at Surgutneftegas refining facility in Russia’s Khanty-Mansi Autonomous Region, leaving at least seven employees injured, RIA Novosti reports. Two of them were taken to the hospital for trauma care, a local health official told the news agency. The incident was caused by detonation inside a pipe cleaning machine, the local Investigative Committee said in a press release. Surgutneftegas is one of the largest companies operating in the oil- and gas-rich part of Russia.