If, in proceedings in juvenile court, it appears probable that an indictable offense has been committed and that the commission thereof caused, or contributed to, the delinquency or dependency of such a child, said court may order the issuance of a warrant for the arrest of such suspected person, and on the appearance of such person said court may proceed to hold a preliminary examination, and in so doing shall exercise all the powers of a committing magistrate.
C93, §709A.4