Isabel Mercedes Celis, missing Ariz. girl, was abducted, police confirm

(CBS/AP) PHOENIX - Police investigating the disappearance of 6-year-old Arizona girl Isabel Mercedes Celis confirmed Tuesday they believe she was abducted.

Pictures: 6-year-old vanishes from Arizona home

Investigators have searched the girl's Tucson, Ariz., home, interviewed more than 500 sex offenders and waded through 1,000-plus tips. So far, they haven't named a suspect.

Police previously characterized the case as a "suspicious disappearance/possible abduction."

Authorities have been searching for the girl since her father reported her missing April 21. Family members have said they last saw her in her bedroom the night before. A window was later found open with the screen pushed aside.

A few days after the disappearance, a neighbor told KVOA-TV that she heard her dogs barking and male voices outside her bedroom window around 6:30 a.m. on the day she was reported missing. The neighbor said there were no sounds that indicated a struggle.

Police declined to comment on her account.

In a news release late last week, police announced that Arizona's child welfare agency was barring Isabel's father, Sergio Celis, from having any contact with his 10- and 14-year-old sons. 

Tucson Police Chief Roberto Villasenor said at a news conference that Isabel's older brothers are "with their mother" and have "not been taken away" by CPS. He noted Sergio Celis is cooperating with the agency's order. Authorities added it's common for the agency to be involved in missing-child cases.

On Monday, investigators released 911 recordings of Celis reporting his daughter missing. He was calm while the girl's mother's reaction was full of emotion.

Celis told a 911 operator that he believed his daughter was abducted.  When asked to explain why he thought that, Sergio Celis said he couldn't and that Isabel wasn't there when the family awoke.

"I want to report a missing person," he said, calmly. "My little girl, who is 6 years old. I believe she was abducted from the house."

The tone of Celis' wife, Rebecca, was frantic. "She's only 6," said the mother as she cried. "Can you please hurry and get somebody over here?"

Police are holding out hope that Isabel is still alive.

Complete coverage of Isabel Mercedes Celis on Crimesider