Cascade Shareholders Approve Merger Agreement with MDU Resources.

BISMARCK, N.D. -- Shareholders of Cascade Natural Gas Corporation (NYSE:CGC) approved a merger agreement with MDU Resources Group, Inc. (NYSE:MDU) in a special meeting of shareholders held today in Seattle, Wash. Approval required the affirmative vote of the holders of more than two-thirds of all shares of Cascade common stock.

"We are very pleased with today's vote," said Terry D. Hildestad, president and CEO of MDU Resources. "Cascade's board of directors unanimously recommended adoption of the merger agreement saying it is in the best interests of their shareholders. The strong affirmative vote demonstrates that shareholders agreed with that recommendation. We look forward to a successful regulatory approval process."

The merger still requires approval from the Washington Utilities and Transportation Commission, the Oregon Public Utility Commission, and various jurisdictions under which MDU Resources' utility divisions operate, as well as clearance under the federal Hart-Scott-Rodino Antitrust Improvements Act of 1976, and the satisfaction of other customary closing conditions. Pending successful approval by all regulatory entities, company officials anticipate the merger to be completed by mid-2007. When the transaction is completed, Cascade common stock will cease to be publicly traded. Cascade will become a wholly owned subsidiary of MDU Resources, continuing to operate as Cascade Natural Gas Corporation.

The definitive merger agreement was initially announced on July 9, 2006. Under the terms of the agreement, MDU Resources will acquire Cascade for $26.50 per share in cash. The transaction has been approved by the boards of directors of both MDU Resources and Cascade.

Cascade's customer base in Washington and Oregon will approximately double the number of MDU Resources' natural gas utility customers. Cascade serves approximately 235,000 customers in 93 communities - 65 of which are in Washington and 28 in Oregon. Cascade's service areas are concentrated in western and south central Washington and south central and eastern Oregon. Cascade's recent customer growth has been more than 4 percent on a compound annual basis. Cascade was founded in 1953 and employs approximately 375 people.

The information in this release includes forward-looking statements, including statements by the president and CEO of MDU Resources Group, Inc., and the statement concerning accretive earnings per share, within the meaning of Section 21E of the Securities Exchange Act of 1934. Although the company believes that its expectations are based on reasonable assumptions, actual results may differ materially. Important factors that could cause actual results to differ materially from those in the forward-looking statements include the ability to obtain necessary regulatory approvals, the satisfaction of closing conditions, the ability to obtain financing and the ability to effectively integrate acquired operations. For a discussion of other important factors that could cause actual results to differ, refer to Item 1A - Risk Factors in MDU Resources' most recent Form 10-K and Form 10-Q.

MDU Resources Group, Inc., a member of the S&P MidCap 400 index, provides value-added natural resource products and related services that are essential to energy and transportation infrastructure. MDU Resources includes natural gas and oil production, construction materials and mining, domestic and international independent power production, natural gas pipelines and energy services, electric and natural gas utilities, and construction services. For more information about MDU Resources, see the company's Web site at www.mdu.com or contact the Investor Relations Department at [e-mail].