WYNNEWOOD, Okla., Sept. 30, 2012 /PRNewswire/ -- CVR Energy, Inc. confirmed today that it launched an immediate internal investigation into the cause of the boiler explosion that occurred at the refinery on Friday evening, fatally injuring one employee and critically injuring another. (Logo: http://photos.prnewswire.com/prnh/20071203/CVRLOGO ) The explosion occurred at approximately 6:20 p.m. as operators were restarting a boiler that had been temporarily shut down as part of the refinery's turnaround process. "I would like to express my deepest sympathy for the employees and families affected by this tragedy," said Jack Lipinski, CVR Energy chief executive officer. "We are conducting a thorough investigation of the incident and cooperating fully with OSHA and the Oklahoma Department of Labor. "Our focus is to determine how this accident occurred and what steps must be taken to avoid a repeat of this incident. We remain committed to providing a safe working environment for our employees and contractors," he said. Damage at the refinery was limited to the boiler. Process units and other areas of the facility were unaffected. Additionally, there has been no evidence of environmental impact. No damage estimates were immediately available. The turnaround, which is a periodic shutdown of the operations, allows for necessary maintenance and upkeep of operating units. The Wynnewood refinery turnaround resumed Saturday. "We want to thank Wynnewood and Garvin County emergency response teams for their rapid response and assistance," said Wayne Leiker, vice president and refinery manager. "We had immediate support from the community, local clergy, the city and first responders. "I especially want to thank our employees and contractors for their support, hard work and dedication during this difficult time," Leiker said. About CVR Energy, Inc. Headquartered in Sugar Land, Texas, CVR Energy, Inc.'s (NYSE: CVI) subsidiary and affiliated businesses operate independent refining assets in Coffeyville, Kan. and Wynnewood, Okla. with more than 185,000 barrels per day of processing capacity, a marketing network for supplying high value transportation fuels to customers through tanker trucks and pipeline terminals, and a crude oil gathering system serving Kansas, Oklahoma, western Missouri, southwestern Nebraska and Texas. In addition, CVR Energy subsidiaries own a majority interest in and serve as the general partner of CVR Partners, LP, a producer of ammonia and urea ammonium nitrate, or UAN, fertilizers.