Sergio Celis, father of missing Ariz. girl Isabel Celis, barred from contact with his sons

(CBS/KPHO/AP) TUCSON, Ariz. - The father of Isabel Mercedes Celis, a missing 6-year-old Tucson girl, is no longer allowed to have contact with his two older sons.

Pictures: 6-year-old vanishes from Arizona home

CBS affiliate KPHO reports that Sergio Celis was prohibited from contact after detectives called Child Protective Services last week with information regarding the welfare of the older Celis children.

Isabel was last seen around 11 p.m. on April 20 when she was getting ready for bed. She was reported missing by her father around 8 a.m. the next morning after he went to wake her up. According to police, the child was not in her room and a bedroom window was opened with the screen removed.

Tucson police reportedly said CPS "instituted certain measures to ensure the continued welfare of the Celis children," but did not elaborate. CPS says the move is common practice when investigating cases of missing children, KPHO reports.

According to KPHO, Isabel's two brothers were turned over to their biological mother, the ex-wife of Sergio Celis.

Complete coverage of Isabel Mercedes Celis on Crimesiderces13 Photos