(a) In cases other than those forwarded to the Attorney General of the United States under paragraph (b) of this section where violations of the labor standards clauses contained in § 5.5 and the applicable statutes referenced by § 5.1 result in underpayment of wages to workers or monetary damages caused by violations of § 5.5(a)(11) or (b)(5), the Federal agency or an authorized representative of the Department of Labor will request that restitution be made to such workers or on their behalf to plans, funds, or programs for any type of bona fide fringe benefits within the meaning of 40 U.S.C. 3141(2)(B), including interest from the date of the underpayment or loss. Interest on any back wages or monetary relief provided for in this part will be calculated using the percentage established for the underpayment of taxes under 26 U.S.C. 6621 and will be compounded daily.

(b) In cases where the Agency Head or the Administrator finds substantial evidence that such violations are willful and in violation of a criminal statute, the matter will be forwarded to the Attorney General of the United States for prosecution if the facts warrant. In all such cases the Administrator will be informed simultaneously of the action taken.