TUCSON, Ariz. (AP) -- Police investigating the disappearance of a young girl from her family's southern Arizona home say child welfare workers went to the household in December. News of the visit surfaced nearly a week after the father of 6-year-old Isabel Mercedes Celis was barred from having any contact with his 10- and 14-year-old sons. Tucson police spokeswoman Sgt. Maria Hawke confirmed the visit Thursday but says she couldn't provide the circumstances that prompted it. State child welfare agency spokeswoman Tasya Peterson declined to confirm the visit. Authorities have been searching for Isabel since her father, Sergio Celis, reported her missing April 21. The child welfare visit was first reported by the Arizona Daily Star on Thursday. Police haven't determined whether Isabel was abducted by a stranger or someone the family knew.