Welf. & Inst. Code, § 625

A peace officer may, without a warrant, take into temporary custody a minor:

(a) Who is under the age of 18 years when such officer has reasonable cause for believing that such minor is a person described in Section 601 or 602, or

(b) Who is a ward of the juvenile court or concerning whom an order has been made under Section 636 or 702, when such officer has reasonable cause for believing that person has violated an order of the juvenile court or has escaped from any commitment ordered by the juvenile court, or

(c) Who is under the age of 18 years and who is found in any street or public place suffering from any sickness or injury which requires care, medical treatment, hospitalization, or other remedial care.

In any case where a minor is taken into temporary custody on the ground that there is reasonable cause for believing that such minor is a person described in Section 601 or 602, or that he has violated an order of the juvenile court or escaped from any commitment ordered by the juvenile court, the officer shall advise such minor that anything he says can be used against him and shall advise him of his constitutional rights, including his right to remain silent, his right to have counsel present during any interrogation, and his right to have counsel appointed if he is unable to afford counsel.