Welf. & Inst. Code, § 329

(a) When a person applies to the social worker to commence proceedings in the juvenile court, the application shall be in the form of an affidavit alleging that there was or is within the county, or residing therein, a child within the provisions of Section 300, and setting forth facts in support thereof. The social worker shall immediately investigate as necessary to determine whether proceedings in the juvenile court should be commenced. If the social worker does not take action under Section 301 and does not file a petition in the juvenile court within three weeks after the application, the social worker shall endorse upon the affidavit of the applicant the decision not to proceed further, including any recommendation made to the applicant, if one is made, to consider commencing a probate guardianship proceeding for the child, and the reasons therefor and shall immediately notify the applicant of the action taken or the decision rendered under this section. The social worker shall retain the affidavit and the endorsement thereon for a period of 30 days after notifying the applicant.

(b) (1) If a social worker receives a referral from the probate court pursuant to Section 1513 of the Probate Code, the social worker shall immediately investigate as necessary to determine whether proceedings in the juvenile court should be commenced.

(2) The social worker shall, within three weeks of the referral, report the findings and conclusions of the investigation, along with any decision made as a result and the reasons for the decision, to the probate court as required by subdivision (b) of Section 1513 of the Probate Code.