DELPHI, Ind. (AP) - Police investigating the unsolved murders of two northern Indiana teenage girls are hoping the anniversary of the crime spurs a wave of tips from the public that can lead them to the killer.

Carroll County Sheriff Tobe Leazenby says State Police and the FBI have increased staffing to field an anticipated increase in tips about the murders of 14-year-old Liberty German and 13-year-old Abigail Williams.

The girls vanished last Feb. 13 while hiking near their hometown of Delphi, about 60 miles (95 kilometers) northwest of Indianapolis. Their bodies were found the next day.

State Police Superintendent Doug Carter plans a news conference in Delphi on Tuesday's anniversary of the teens' disappearance to renew investigators' call for tips.

Leazenby says the double-murder investigation is far from becoming a cold case.

Days after the murders, local, state and federal authorities released a grainy cell phone image -- taken by Libby -- of a man they are calling a suspect in the case.

They also released more information recorded by Libby's phone: audio of three words uttered by a voice authorities say belongs either to the man in the photograph, or another individual who was likely involved in the murders. 

The audio contains only one phrase: "Down the hill."

To hear a recorded loop of the audio of the suspect, CLICK HERE

The police tip line for the case is 844-459-5786. Tips can also be reported by emailing Abbyandlibbytip@cacoshrf.com or visiting the State Police website on Delphi killings.

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