Police are going door-to-door in search of new tips in the case of an Arizona 6-year-old who vanished almost two years ago.

Isabel Celis was reported missing by her father in 2012. She was last seen in the bedroom of her Tucson home.

Authorities say they believe that the person who abducted Celis was very familiar with the home’s layout.

More than 50 officers have visited about 350 homes and apartment units in the area to question people about the case.

Fox News contributor Rod Wheeler says authorities often go back to interview people later in order to see if their stories have changed over time, which could indicate that they’re lying.

Watch the video above for more on the case.