Becky and Sergio Celis tell the Arizona Daily Star that they hope renewed efforts by Tucson police will give clues as Isabel Celis' disappearance reaches the two-year mark Monday.
Eight detectives were assigned in January to review the case and conduct new interviews.
Becky Celis says she someone may remember something with the passage of time.
Sergio Celis called police the morning of April 21, 2012 after finding 6-year-old Isabel wasn't in her bedroom.
Police canvassed the girl's neighborhood, nearby parks and even a landfill.
They have declined to say whether the child is believed to still be alive.