The FBI is planning to exhume the body of a young woman whose unsolved murder was examined in the Netflix documentary The Keepers.

Joyce Malecki, 20, went Christmas shopping near Baltimore in November 1969 and never came home.

Her body was found on a nearby military base days later. She had been strangled.

The case received renewed attention after The Keepers was released in 2017, raising questions about whether Ms Malecki's disappearance was linked to the murder of a nun.

Sister Cathy Cesnik was found dead from blunt force trauma after she went shopping and never returned.

The documentary questioned whether Sister Cesnik was killed by Father Joseph Maskell, a Catholic priest at the school where they both worked, because she knew he was sexually abusing students.

His body was exhumed in 2017 but the DNA testing didn't reveal a match and the case remains unsolved.

There was fresh hope for a lead in Ms Malecki's case earlier this year, when authorities announced they had solved another homicide case: 16-year-old Pamela Conyers, who went missing in 1970 from the same shopping mall as Ms Malecki and also died from strangulation.

Investigators used relatively new DNA technology and genealogy research to identify a suspect in her death: Forrest Clyde Williams III, who died in 2018 of natural causes.

When they pinned Pamela's killing on Williams, officials said they didn't have evidence connecting him to either of the other unsolved homicides.

It appears investigators are now looking to extract DNA from Ms Malecki's body, said Kurt Wolfgang, executive director of the Maryland Crime Victims Resource Centre.

He said while it's not clear what they are looking to find out, the timing could suggest a link to Williams.

Mr Wolfgang said relatives will be allowed to attend the exhumation, which will otherwise be closed to the public.

"They want justice out of this thing," said Mr Wolfgang, whose non-profit has been working with the Malecki family.

"Even though it was 54 years ago, it would certainly help them to know what happened."

An advocate for the Malecki family confirmed the exhumation was tentatively planned for Thursday.

A spokesperson for the FBI's Baltimore Field Office declined to comment, citing "respect for the ongoing investigation".