"Green River Killer" Gary Ridgway was booked into the King County Jail in Washington state Monday morning, though reasons for the transfer are unknown, according to reports.

FOX 13 in Seattle reported that Ridgway, who pleaded guilty in 2003 to murdering 49 women in King County from 1982 to 1998, was booked into the jail just after 10:40 a.m. on an institutional hold put in place by the King County Sheriff’s Office.

The notorious serial killer was serving 49 consecutive life sentences at the Washington State Penitentiary in Walla Walla, without the possibility of parole.

The transfer to a lower-level jail has raised questions, though officials have not provided details as to why Ridgway was moved.

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Fox News Digital has reached out to the King County prosecutor’s office for comment.

In November 2003, Ridgway pleaded guilty to the murder of "Bones #20," Denise Bush, and Shirley Sherrill, along with 45 other victims. He also later pleaded guilty to the murder of the 49th victim. 

Throughout the 1980s, Ridgway terrorized and instilled fear across the state of Washington. He was convicted of killing 49 women but has confessed to 71 murders. However, investigators believe that he killed more victims.

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In December, authorities identified one of the victims as 15-year-old Lori Anne Razpotnik, who ran away from her home in Lewis County in 1982.

Razpotnik’s remains were found in 1985, on a road embankment in Auburn, south of Seattle, alongside the remains of two other victims. Investigators could not determine who those victims were, and the remains were listed as "Bones 16" and "Bones 17."

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Bones 16 was identified through DNA testing in 2012 as Sandra Majors, but the identity of Bones 17 remained unknown until a forensic genetic genealogy firm, Virginia-based Parabon Nanolabs, was able to develop a new DNA profile and determine they belonged to Razpotnik.

Razpotnik's mother provided a DNA sample that confirmed the results, the King County Sheriff's Office said.

After authorities linked Gary Ridgway to the killings through DNA evidence in 2001, he led them to the site where the three victims had been found. 

Bones 16 and Bones 17 were among the 48 slayings he pleaded guilty to in 2003. Many of his victims were young female runaways or sex workers.

Fox News Digital’s Stepheny Price and The Associated Press contributed to this report.