Iowa Code § 901D.9
An allegation that a participant failed a test, refused to submit to a test, or failed to appear for testing shall be communicated ex parte by the participating jurisdiction, a law enforcement agency of the participating jurisdiction, or the participating jurisdiction's third-party designee to a magistrate as soon as practicable. A magistrate who receives such a communication may order the participant's immediate incarceration pending a hearing on the allegation but lasting no longer than twenty-four hours after the issuance of the order, or if the participant failed to appear for testing as scheduled, the magistrate may issue a warrant for the arrest of the participant for a violation of the terms of bond, pretrial release, sentence, probation, or parole, as applicable.
Iowa Code § 901D.9