New York (CNN) -- Investigators and rescue teams will continue their search Friday for a missing 13-year-old Texas girl, focusing near a densely wooded area and along the Colorado River.
Meanwhile, Hailey Dunn's mother, Billie Dunn, told HLN's Nancy Grace that she and her live-in boyfriend, Shawn Adkins, both failed polygraph exams.
Adkins was the last person to see the eighth-grade cheerleader on December 27 at Dunn's home in Colorado City, according to local reports.
Colorado City -- a rural central Texas town -- is about 70 miles west of Abilene.
Hailey reportedly told Adkins she was going to visit her father and then a friend. Hailey's father, Clint Dunn, says she often came to his home but did not on that day.
Dunn said she took the polygraph test after she was informed that Adkins had failed.
Woodrow Tripp, a polygraph expert, told Nancy Grace that troubles him.
''That absolutely would cause major problems emotionally as she's administered one. You want to try to minimize that as much as possible," Tripp said.
Dunn did not say who administered the exam, during which she says she was asked if she knew anything about or caused Hailey's disappearance and whether she feared any questions.
The night Hailey vanished, Dunn says she thought her daughter was sleeping over at a friend's house.
Asked why she did not confirm Hailey's location before going to bed that night, Dunn said, ''I just don't have an answer for that. I wish I would have called to tell her goodnight.''
Dunn says police questioned her for more than 10 hours on Wednesday.
She met Adkins on the MySpace social networking site more than two years ago, and he moved in with her several months ago.
Police initially considered Hailey a runaway, but the situation is now a missing person case. A Texas Amber Alert has not been issued, reportedly because no one saw Hailey being abducted.
Hailey is 5-foot-2 and weighs 120 pounds. She has hazel eyes and brown hair with blond streaks.
When she disappeared, she was wearing navy blue sweatpants, a light colored short sleeve T-shirt, and pink and white tennis shoes.