Terry Jones, the interim police chief in Aurora, Colo., says investigators have no suspects but the girl's father and his girlfriend are "people of interest that we would like to interview."
"We believe she is dead and she was murdered," Jones told the Denver Post.
He said police received information Wednesday "from an individual close to the family" that led them to believe that the child, Aaroné Thompson, had been killed in the house within the past 18 months. No body had been found.
The search for Aaroné began Monday when her father, Aaron Duane Thompson, told police she had run away.
Police meanwhile took seven children, ages 8 to 15, from the home and placed them with Arapahoe County child protective services.