Infamous murder investigation of two girls heading in 'new direction'

One of the nation's most recent infamous unsolved murder investigations is heading in a "new direction."

Indiana State Police said in a statement Friday that new information in their inquest into the murder of two teenage girls in Delphi, Indiana, in February 2017 will be shared at a press conference on Monday.

The update will be held "to share information with the media and public about the new direction of the Delphi homicide investigation."

Police shared no further information into what the new evidence might be, or why they were changing directions in the investigation.

Friends Abigail Williams, 13, and Liberty German, 14, both middle schoolers, vanished on a hiking trail near Delphi on Feb. 13, 2017. Their bodies were found one day later about a mile from where they were last known to be on the trail.

Authorities have not released information about how the girls died.

The murders have also been called the "Snapchat murders" -- named as such due to a photo shared by German of Williams walking on an old railroad bridge during their hike on the day they disappeared.

"We're all frustrated," Abby's mother, Anna Williams, told ABC News in February, just before the second anniversary of the children's deaths. "It might still feel like we're in the same place, but I think of how many tips we've gone through, how many are still out there, still coming in, and I still have hope that we are on the right track."

Authorities released a grainy photo of a man they believe could be a suspect in the girls' killings and an audio recording found on Libby's phone with a man saying "down the hill" in the days following the murders. Police later released a composite sketch of the man they believe to be in the photo.

No definitive match for the suspect has ever been found, despite thousands of tips and over $200,000 in reward money being offered.

Just before the one-year anniversary of the teens' murders, a sheriff's office in Bledsoe County, Tennessee, wrote on Facebook that the "FBI has extended the search" for Abby and Libby's killer or killers into southeastern Tennessee. The report was almost immediately shot down by the Indiana State Police, saying the search was still "nation wide." Bledsoe County authorities blamed the post on a "misunderstanding."

Police arrested an Indiana man in September 2017 that authorities initially said could be related to the Delphi killings. Daniel Nations, 31, was taken into custody in Colorado after threatening people near a hiking trail with a hatchet, police said.

Indiana State Police nonetheless downplayed the arrest at the time, simply saying they were treating it like any other possible tip. In a press conference on the one-year anniversary of the killings, state police conceded, despite their interviewing Nations, he was not someone "they care a whole lot about" in relation to the crime.

ABC News' Emily Shapiro contributed to this report.