DELPHI, Ind. (AP) - Police investigating the unsolved murders of two northern Indiana teenage girls are hoping the crime's one-year anniversary 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.

RELATED: Audio clip released in Delphi, Ind. double homicide

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.

RELATED: Reward increased for information in Delphi double homicide

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

RELATED: Hear the audio clip that police released of the suspect