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UPDATE: Police confirmed on Sunday that Richard Allen is not cooperating with their investigation into the murders after being taken into jail. Original story below.

DELPHI, Ind. — Multiple sources indicate that a man named Richard Allen was booked into the Carroll County Jail Friday in connection with the Delphi murder investigation.

Allen, 50, has been moved to a state facility for his safety, sources said.

Earlier, law enforcement sources told FOX59 that a major development was in the works in the 2017 murders of Libby German and Abby Williams, with a news conference scheduled for Monday with additional details.

Richard Allen

The teens disappeared on the Monon High Bridge on Feb. 13, 2017. They were reported missing, and their bodies were found around noon on Feb. 14, 2017.

The high-profile murder case has gone unsolved for more than five years, generating mountains of online speculation about the identity of the killer.

Police released two different sketches of potential suspects. Key evidence included audio and photos from Libby German’s phone, with police releasing an audio clip of a man saying, “Down the hill.”

Court documents unearthed by the Murder Sheet Podcast over the summer showed an FBI agent believed there was probable cause to search the property of Ron Logan, who owned the land on which the girls’ bodies were found.

Authorities searched the property on March 17, 2017.

The search warrant revealed additional details about the investigation, including that the recording in which the “down the hill” audio originally lasted 43 seconds, only a fraction of which has been released to the public.

Additionally, investigators found a large amount of blood at the scene, leading them to believe the perpetrator would’ve gotten blood on their hands or clothing. The individual may have taken a “souvenir” from the crime scene, according to court documents, and may have also “moved and staged” the teens’ bodies.

According to the warrant, the investigating agent believed Logan’s physical build matched that of the man who appeared in the video from Libby’s phone. His voice was “not inconsistent” with the recording released to the public.

Logan also lied about his alibi, according to investigators. He was never named as a suspect or charged in connection with the Delphi case. He has since died.

The case, which has gained national attention, has picked up momentum recently, with authorities revealing a social media profile called “anthony_shots” had interacted with Libby.

Police traced that profile to an individual named Kegan Kline, who was being investigated in connection with a child exploitation case. He has never been charged or named as a suspect in connection with Delphi murders.

Kline has been questioned about the case. His trial on 30 counts of possession of child pornography is going through the court system.

In recent months, Indiana State troopers have been searching the Wabash River in Peru potentially looking for evidence tied to the case.