Exhibit 23(c) CONSENT OF ENGINEER We hereby consent to the incorporation by reference in this registration statement of the reference to our report, dated May 9, 1994, which appears in the MDU Resources Group, Inc. Annual Report on Form 10-K for the year ended December 31, 1997. WEIR INTERNATIONAL MINING CONSULTANTS /s/ Dennis N. Kostic Des Plaines, Illinois February 18, 1999