MDU Resources Group, Inc. (NYSE:MDU) announced today that it has acquired Star Aggregates, Inc., a leading aggregate producer in Cheyenne, Wyo.

Star Aggregates will become part of Knife River Corporation, the construction materials and mining subsidiary of MDU Resources. Financial details of the acquisition were not disclosed. MDU Resources anticipates the acquisition will be accretive to 2007 earnings per share.

“The acquisition of Star Aggregates establishes our corporation in the material supply and construction business in the growing metropolitan area of Cheyenne, Wyo.,” said Terry D. Hildestad, president and chief executive officer of MDU Resources. “It is our intention to continue to acquire successful and well-managed companies, like Star, to increase our presence in the construction materials industry.”

Star Aggregates has permitted aggregate reserves in the Cheyenne market. Its services include highway construction, earth work and asphalt paving. In addition, it supplies aggregate and asphalt to third-party customers. The company employs approximately 85 individuals.

“We are proud to welcome the employees and management team of Star to Knife River,” said William Schneider, president and chief executive officer of Knife River. “Star is an excellent addition to our company and will complement our existing operations in Wyoming.”

Star Aggregates will operate as part of Knife River’s Mountain Region, which includes operations in Billings, Belgrade, Kalispell, Missoula and Polson, Mont.; and Casper, Wyo.

The information in this release includes forward-looking statements, including statements by the president and chief executive officer of MDU Resources and the president and chief executive officer of Knife River, as well as the statement with respect to the anticipated effect of the transaction upon 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 effectively integrate the 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, operating in three core lines of business; Energy, Construction Materials and Utility Resources. MDU Resources includes natural gas and oil production, natural gas pipelines and energy services, construction materials and mining, construction services, and electric and natural gas utilities. For more information about MDU Resources, see the company's Web site at www.mdu.com or contact the Investor Relations Department at investor@mduresources.com.

Contacts:

  Financial: 
      Vernon A. Raile
      Executive Vice President, Treasurer and Chief Financial Officer
      (701) 530-1003

     Phyllis A. Rittenbach
     Director of Investor Relations
     (701) 530-1057

  Media:  
     Rick Matteson
     Director of Communications and Public Relations
     (701) 530-1700

     Art Thompson
     Senior Public Relations Representative
     (701) 530-1054