Isabel Celis was last seen by her parents who put her to bed Friday around 11 p.m., KVOA-TV, Tucson, reported.
At a news conference Monday, Tucson Police Chief Roberto Villasenor said law enforcement officials were looking into more than 100 leads in the case, which was being treated as a possible abduction.
Villasenor said police worked with FBI canine units, which had given investigators some direction.
Police said a broken screen on a window in Isabel's bedroom could indicate a point of entry for a possible kidnapping, but Villasenor stressed it is not "a definitive point of entry," the Arizona Daily Star reported.
Hundreds of people participated in a candlelight vigil organized by co-workers of the girl's mother Sunday night, praying for Isabel's return.