Cal. Welf. & Inst. Code § 340

Whenever a petition has been filed in the juvenile court alleging that a minor comes within Section 300 and praying for a hearing thereon, or whenever any subsequent petition has been filed praying for a hearing in the matter of the minor and it appears to the court that the circumstances of his or her home environment may endanger the health, person, or welfare of the minor, or whenever a dependent minor has run away from his or her court ordered placement, a protective custody warrant may be issued immediately for the minor.