The parents of Lisa Irwin say she was kidnapped last Tuesday from their home, and a window had been tampered with the night she disappeared.
Her parents said someone must have crept into their home while the child's mother and brothers slept.
An officer was also seen walking around the house on Monday, but he did not speak to media.
Police say they're still operating their 24-hour command center, doing everything they can to find the child.
Although leads are coming in "all the time," Capt. Steve Young said, investigators still have nothing solid so far and no suspects despite an extensive search of the family's quiet neighborhood, including their home and neighbors' houses, a nearby woods, sewers and a Kansas landfill.
The Associated Press contributed to this report.