Energy Industry Executive Paul Prager and Natural Gas Partners to Acquire North American Power Business of MDU Resources in $636 Million Transaction

Energy industry executive Paul Prager and Natural Gas Partners ("NGP”), the leading investment franchise in the energy industry, today announced that they have entered into an agreement to acquire the domestic independent power production and power development business units of MDU Resources Group, Inc. (NYSE: MDU) in a transaction valued at $636 million. The business being acquired includes Centennial Power, Inc. ("Centennial Power”) and Colorado Energy Management, LLC ("Colorado Energy Management”). Centennial Power and Colorado Energy Management will become part of a new company formed by Mr. Prager and NGP to engage primarily in the ownership, operation and acquisition of coal-fired, natural gas-fired and wind generation in North America. Centennial Power’s generating assets include 603 MW of electric generating capacity located in Montana, Colorado, California and Georgia. The assets are fully contracted under mid- to long-term power purchase and sale agreements, and include coal-fired, natural gas-fired and wind-powered generation. Colorado Energy Management provides design, construction, operation and maintenance services to energy partners. Given the inherent strength of the Centennial Power generation portfolio, the operational capabilities of the new ownership group and the potential for investor follow-on capital, the new company will be ideally positioned to be competitive in all aspects of the business, from greenfield development of new electric generation to acquiring additional clean coal technology-based, gas and wind power projects. Paul Prager stated, "This is a great time to be in the power industry and we are delighted to acquire the best-in-class operating assets at Centennial Power and Colorado Energy Management. The combination of our team’s expertise and the capital strength provided by NGP, one of the world’s most-respected energy investors, together with the fine people of Centennial Power and Colorado Energy Management will allow us the opportunity to build a responsible and successful power company.” William Quinn, Managing Partner of Natural Gas Partners, said, "We are extremely excited about the acquisition of Centennial Power and Colorado Energy Management. NGP is fortunate to be able to partner with Paul Prager and his team to acquire and further build a premier and diversified portfolio of electric generating assets.” The officers of the new company are Paul Prager, Chairman, CEO and President; Douglas Halliday, Executive Vice-President and COO; Christopher Ryan, Executive Vice-President and CFO; and Nazar Khan, Senior Vice President, Development and Acquisitions. Mr. Prager and his team were instrumental in the successful growth and subsequent sale of CES Energy Assets in a series of transactions to Direct Energy, Energy Investors Fund and J- Power. The team also controls Trinity Power Ltd. ("Trinity”), which owns a 225 megawatt gas fired electricity generating facility located in the Republic of Trinidad & Tobago. Trinity enjoys a 30 year contract to sell electricity to T&TEC, the Trinidad state utility, and is subject to a further guarantee by the Trinidad government (S&P/Moodys rating: A-/Baa1). Barclays Capital and Goldman, Sachs & Co. have committed to provide the debt financing to support the transaction. Completion of the transaction, which is expected in June 2007, is subject to fulfillment of regulatory approvals and conditions established within the agreement. Barclays Capital is serving as financial advisor to Mr. Prager and NGP with respect to this transaction, and Paul, Weiss, Rifkind, Wharton & Garrison LLP is serving as legal counsel. About Paul Prager A graduate of the U.S. Naval Academy, Mr. Prager has extensive experience in international shipping, commodity trading and power development. In 1985, Mr. Prager joined Salomon Brothers Inc. as a trader. In 1987, he founded and served as Managing Director of Davco Oil, a crude oil and crude product physical and derivatives trader. Since 1990, Mr. Prager has focused exclusively on development, operation and ownership of energy facilities and maritime assets. Mr. Prager currently serves as a member of the Board of the U.S. Naval Academy Foundation. About Natural Gas Partners Founded in 1988, the Natural Gas Partners private equity fund complex is a family of funds with over $3 billion of total capital under management since inception. The funds invest private equity capital in various sectors of the energy industry, including oil and gas production, midstream and oilfield service companies and co-invest in direct oil and gas property interests alongside portfolio companies. Natural Gas Partners is managed by Irving, Texas based NGP Energy Capital Management, the premier investment franchise in the energy industry. In addition to the Natural Gas Partners complex, NGP’s $4.2 billion investment platform includes NGP Capital Resources Company (NASDAQ: "NGPC"), a publicly-traded business development company that focuses on providing senior debt and mezzanine capital to the energy industry, NGP Energy Technology Partners, L.P., a fund investing growth equity capital in companies providing technology-related products and services to the oil and gas, power and alternative energy sectors and NGP Midstream & Resources, L.P., a fund making direct investments in selected areas of the energy infrastructure and natural resources sectors. Natural Gas Partners may be contacted at (972) 432-1440 or www.naturalgaspartners.com.