Authorities say they have received more than 500 tips regarding the murders of Liberty German, 14, and Abigail Williams, 13, in Delphi, Indiana.
Liberty and Abigail were found dead near a hiking trail on Feb. 14, according to ABC News. A family member dropped them off for a hike on Feb. 13, and their families reported their disappearance to the police when the girls did not return home.
The FBI is offering a $41,000 reward for information that may help solve the case, according to WXIN. Local authorities and community leaders are also offering $50,000, ABC News notes.
Authorities are working with two main pieces of evidence, both of which were retrieved from Liberty's cellphone, WXIN reports. One is an audio recording of a man's voice saying, "down the hill," and the other is a photo of a man on the same trail where the girls were walking.
Indiana State Police say the man in the photo from Liberty's phone is their primary suspect, according to ABC News. The man was dressed in blue jeans, a blue jacket and a hoodie, and was photographed on a trail around the same time the two girls disappeared.
Officials have also made pleas to the community to help find the killer.
"Someone knows who this individual is," said Indiana State Police Superintendent Douglas Carter. "And if you're watching, we'll find you."
On Feb. 22, the FBI outlined ways to identify possible suspects in the area, which included a "change in normal routine which might include missing work or other engagements."
"Often someone in the community will unknowingly be associated with the individual or individuals who committed the crime," the FBI said in the statement.
"Just think if you had an interaction with an individual who inexplicably canceled an appointment that you had together," FBI assistant special agent Gregory Massa said on Feb.22, according to ABC News. "Or an individual called into work sick and canceled a social engagement. At the time, they gave what would have been a plausible explanation."