TUCSON, AZ - The parents of a 6-year-old Tucson girl missing for nearly two weeks have been given lie detector tests.
Tucson police say Sergio and Becky Celis took the polygraph test within the first few days of the investigation.
Police say the polygraph test results are being withheld and they are part of an investigative tool used by detectives.
The couple spoke to reporters Friday following an appearance on NBC's "Today" show where they pleaded for the return of their daughter.
The missing girl's parents became emotional during an approximately 40-minute interview with Tucson reporters.
"We just don't understand, we don't understand who would take her, there's no reason to take her," Becky Solis said.
The couple says they understand the scrutiny placed on them as Tucson police try to find Isabel Mercedes Celis.
Emotions swelled when reporters asked the couple what they would tell their daughter.
"We miss you so much Isabel, your brothers miss you so much, we want you back, we're looking for you, we will not stop looking for you ," Sergio said.
The parents say they last saw Isabel in her bedroom the night of April 20 and discovered her missing the next morning. Police say a window was found open with the screen pushed aside.