Chilling audio released of the man suspected of killing two teenage girls

Police have released chilling audio footage of the man they believe may be responsible for murdering two teenage girls.

Abigail Williams, 13, and Liberty German, 14, were found dead last week after failing to return from a walk near the Monon High Bridge in Indiana, USA.

The teenagers were active on social media in the hours before their deaths, with Liberty even posting an eerie photo of Abigail walking along the secluded railway track.

Authorities then released a picture last week of a man they were hoping to speak to in relation to the murders.

Dressed in blue jeans, a blue coat or jacket and a hoodie, they said he may have information about the murder.

Now, police have released an audio file taken from Liberty Germna's phone, saying she had 'the presence of mind' to turn her video camera on.

While the tape is mostly inaudible, a man can be heard saying 'down the hill.' Police have now asked the public to help identify the voice.

'This young lady is a hero. There's no doubt,' Indiana State Police Sgt. Tony Slocum said, saying the recording has provided them with their best information.

'We are actively looking for this person. This person is our suspect.'

Police said that it was possible the voice belongs to the man in the photo but also said more than one person could be involved.

You can listen to the recording below: