Eerie links emerge between the 'Snapchat murders' and an unsolved 2012 double murder.

Authorities are investigating eerie similarities that have been drawn between the murders of Liberty German, 14, and her 13-year-old friend Abigail Williams in February and an unsolved double murder from 2012.

The bodies of Libby and Abby were found just one day after they went missing while on a hike at Monon High Bridge near Delphi in Indiana.

Their deaths have been dubbed the 'Snapchat murders' after Libby posted a series of final images on social media before their disappearance.

Residents have raised concerns over the parallels the crime - which remains unsolved despite police offering a reward and releasing visual and audio evidence - has with the murder of two cousins just a few hundred kilometres away.

Ten-year-old Lyric Cook and her eight-year-old cousin Elizabeth Collins vanished on July 13, 2012, while riding their bikes on a trail.

A pair of hunters discovered their bodies in December, which were too decomposed to determine how they had died.

More then four years later, no arrests have been made.

Both sets of girls were murdered on hiking trails, and left in the woods on the 13th day of the month.

Elizabeth's father, Drew Collins, told KWWL he called detectives working on his daughter's case as soon as he heard about the Delphi murders.

"I wanted to make sure they were looking at it and they were already 10 steps ahead of me, looking at it. They contacted Indiana State Police," he said.

Despite the similarities between the two cases, Collins said he hasn't got his hopes up for them to be connected.

"Chances are, it probably isn't the same person, even though there are similarities. It has been a roller coaster ride, so I don't get too excited."

He offered his thoughts to the families of those involved.

"My heart just breaks for the families. I don't know what they are going through. I know what I went through and our family went through," he said.

"It is just very hard, It doesn't get easier."