Tucson Police Department/Landov
05/03/2012 at 02:00 PM EDT
Sergio and Becky Celis believe police should take the focus off of them during the investigation of their missing daughter
"We do feel sometimes that they're wasting time with us," Isabel's dad Sergio tells the Today
show. "[But] we know we have to be under, you know, scrutiny, absolutely understandable. … We're desperate in finding out information. We're extremely frustrated it's taking so long."
The Tucson, Ariz., parents, who took polygraph tests, have cooperated with police in the search for Isabel, 6, who vanished from her bedroom after being put to bed on April 20.
The scrutiny, Becky says, is "nothing we can't handle," adding she believes police are doing everything they can to solve the case.