The remains were found March 16 near Lake J.B. Thomas in Scurry County, KWTX.com, Waco, reported.
Scurry County Sheriff Trey Wilson said Hailey's disappearance and cause of death are still under investigation.
Police had been searching for the 13-year-old for more than two years. More than 100 billboards featuring Hailey's picture and information about her case were posted along highways in western Texas and other states.
Billie Jean Dunn was charged and convicted in the case for lying about the whereabouts of Shawn Adkins, her boyfriend, on the night of Hailey's disappearance. Dunn was sentenced to 90 days in jail and probation for one year for making a false report to law enforcement.
Dunn and Adkins, who has not been charged in the case, have both denied involvement in Hailey's disappearance.
Notable deaths of 2014 [PHOTOS]