LOUISVILLE, Ky. (WDRB) -- The lead detective investigating the killings of two Indiana girls said they have more audio of the killer's voice. 

Abby Williams and Libby German were killed in February while out on a walk at the Delphi historic trails. 

Police released an audio clip recorded on Libby's cell phone of what's believed to be the killer's voice saying "Down the Hill." Police now say they have even more from her phone. 

"We have only released a portion of it," said Sgt. Jerry Holeman with Indiana State Police. "There are some others we think could help us, but again, protecting the integrity of the investigation is key. So we cant release everything, because there are certain people that know the details."

Police also said the recovered DNA evidence from the crime scene. 

Several people say they saw the killer on the trails the day Abby and Libby died, which helped police develop a composite sketch released last month. 

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