Cal. Welf. & Inst. Code § 628
(a)
(1) Upon delivery to the probation officer of a minor who has been taken into temporary custody under the provisions of this article, the probation officer shall immediately investigate the circumstances of the minor and the facts surrounding their being taken into custody and shall immediately release the minor to the custody of their parent, legal guardian, or responsible relative unless it can be demonstrated upon the evidence before the court that continuance in the home is contrary to the minor’s welfare and one or more of the following conditions exist:
(2) The probation officer’s decision to detain a minor who is currently a dependent of the juvenile court pursuant to Section 300 or the subject of a petition to declare the minor a dependent of the juvenile court pursuant to Section 300 and who has been removed from the custody of their parent or guardian by the juvenile court shall not be based on any of the following:
(d)
(2) If the minor is detained and the probation officer has reason to believe that the minor is at risk of entering foster care placement, as defined in paragraphs (1) and (2) of subdivision (d) of Section 727.4, then the probation officer shall conduct, within 30 days, an investigation in order to identify and locate all grandparents, adult siblings, and other relatives of the child, as defined in paragraph (2) of subdivision (f) of Section 319, including any other adult relatives suggested by the parents. The probation officer shall provide to all adult relatives who are located, except when that relative’s history of family or domestic violence makes notification inappropriate, within 30 days of the date on which the child is detained, written notification and shall also, whenever appropriate, provide oral notification, in person or by telephone, of all the following information:
(3)
(A) The probation officer shall use due diligence in investigating the names and locations of the relatives, including any parent and alleged parent, pursuant to paragraph (2), including, but not limited to, asking the child in an age-appropriate manner about any parent, alleged parent, and relatives important to the child, consistent with the child’s best interest, and obtaining information regarding the location of the child’s parents, alleged parents, and adult relatives. Each county probation department shall do both of the following: