2008-05-09 22:35:10 -

- MDU Resources Group, Inc. (NYSE:MDU) announced today that it has acquired Yarbrough's Dirt Pit, Inc., doing business as Yarbrough's Material & Construction (Yarbrough), a leading aggregate supplier and ready-mix concrete producer near Sour Lake, Texas, located approximately 25 miles west of Beaumont.

Yarbrough will become part of Knife River Corporation, the construction materials and contracting subsidiary of MDU

Resources. Financial details of the acquisition were not disclosed. MDU Resources anticipates the acquisition will be accretive to 2008 earnings per share.

"The addition of Yarbrough strengthens our corporation in the construction materials business in an area that is experiencing strong industrial and commercial growth," said Terry D. Hildestad, president and chief executive officer of MDU Resources. "We intend to continue acquiring successful and well-managed companies, like Yarbrough, to increase our presence in the construction materials industry."

Yarbrough serves the southeast Texas market, primarily the Beaumont and Port Arthur area, with an aggregate distribution yard and ready-mix plant. Yarbrough distributes in excess of 300,000 tons of aggregate annually.

"Knife River is proud to welcome the employees and management team of Yarbrough," said Bill Schneider, president and chief executive officer of Knife River. "This is an excellent addition to our company and will complement our existing operations in southeast Texas."

Yarbrough will operate as part of Knife River's South Region, which includes operations in Central and East Texas.

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.

MDU Resources Group, Inc.
Financial:
Vernon A. Raile, 701-530-1003
Executive Vice President, Treasurer and Chief Financial
Officer
or
Phyllis A. Rittenbach, 701-530-1057
Director of Investor Relations
or
Media:
Rick Matteson, 701-530-1700
Director of Communications and Public Relations
or
Pamela Trhlik, 701-530-1054
Senior Public Relations Representative