AURORA, Colorado (AP) -- Police used dogs to search for the body of a missing 6-year-old girl Friday, a day after authorities said they believe the child had been killed and that her father and his girlfriend were "persons of interest" in the case.Aaron Thompson reported his daughter Aarone missing on Monday, but police accused him of lying and said she may have been killed more than a year ago.The search for the missing girl was called off late Wednesday and became a homicide investigation after a tip that someone had killed Aarone at her home, interim Police Chief Terry Jones said.Aarone should be celebrating her seventh birthday in a couple of weeks, but she was not enrolled in school, and investigators could not find any pictures of her older than age 4, Jones said."Over a period of time -- up to possibly a year and a half ago -- Aarone Thompson may have been murdered," he said.While cadaver dogs were brought in Friday to search the property and possibly other sites, investigators were talking to the other children who lived in the home.Seven children, ages 6 to 15, were taken into protective custody, Jones said. Police also have been speaking with Aarone's grandparents and her mother, who lives in Michigan.Jones said investigators had not yet interviewed Aarone's father or his girlfriend, Shely Lowe, both of whom were described by police as "persons of interest."Attorney Leta Holden, identified by a family spokesman as the couple's lawyer, said she had agreed to assist the family but had not been retained as legal counsel."The family is deeply concerned about the well-being of Aarone and the efforts being made for her safe return home," Holden said Friday.Thompson has denied any involvement in his daughter's disappearance, according to the family spokesman, Sam Riddle. Riddle said he has "grave concerns" about the police handling of the case and questioned why the search for the girl was called off."This police chief better ... have a substantial body of evidence to back up this statement that Aarone was murdered," Riddle said.Thompson told police on Monday that Aarone had left after an event that upset her. That was a lie, Jones said, declining to elaborate."The investigation leads right back to this home," Jones said.After reporting his daughter's disappearance, Thompson had also asked the public for help, telling KMGH-TV: "I'm scared for her safety. ... If anybody has information, please contact the police to bring my baby girl home."Veronica Boivin, who lives a few houses from the home, surrounded by a neat yard in a cul-de-sac, said she rarely saw children outside except when they were going to and from school or doing yard work."I don't ever remember seeing that little girl. I remember older kids," she said. "They're always cooped up into their home."Nearby, someone had tied a handwritten sign to a fence. Beneath it were a candle and a stuffed white unicorn."Aarone we all miss you," the sign stated. "We all love you. Please come home."Copyright 2005 The Associated Press. All rights reserved.This material may not be published, broadcast, rewritten, or redistributed.