If a petition to determine custody of a child has been filed in a court of competent jurisdiction, or if a temporary order pending determination of custody has been entered in accordance with Chapter 3 (commencing with Section 3060), and the whereabouts of a party in possession of the child are not known, or there is reason to believe that the party may not appear in the proceedings although ordered to appear personally with the child pursuant to Section 3430, the district attorney shall take all actions necessary to locate the party and the child and to procure compliance with the order to appear with the child for purposes of adjudication of custody. The petition to determine custody may be filed by the district attorney.