Cal. Welf. & Inst. Code § 328
(a) If the social worker has cause to believe that there was or is within the county, or residing in the county, a person described in Section 300, the social worker shall immediately make any investigation the social worker deems necessary to determine whether child welfare services should be offered to the family and whether proceedings in the juvenile court should be commenced. If the social worker determines that it is appropriate to offer child welfare services to the family, the social worker shall make a referral to these services pursuant to Chapter 5 (commencing with Section 16500) of Part 4 of Division 9. An inference regarding the credibility of the allegations or the need for child welfare services shall not be drawn from the mere existence of a child custody or visitation dispute.
(b)
(1) The State Department of Social Services shall submit a report to the Legislature that includes all of the following data: