The police chief of a Southern California city at the time a young woman was murdered in 1966 said the killing could have been related to the Zodiac Killer murders that occurred hundreds of miles away, according to a group that recently claimed to have unmasked the notorious murderer.

But the police department's current stance is that the slayings are not related.

The Case Breakers, a group comprised of former police investigators, military intelligence analysts and journalists, claimed an Oct. 20, 1969 letter from then-Riverside Police Chief Lambert "Curly" Kinkead to Napa County Sheriff Earl Randol said the murder of Cheri Jo Bates followed a "similar M.O. of your ‘Zodiac’" suspect.

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San Francisco police circulated this composite of the Bay Area's "Zodiac" killer. The FBI said the case remains open after an independent group said it has identified the killer. (Getty Images)

Napa County was where college students Cecelia Shepard and Bryan Hartnell were stabbed while picnicking at Lake Berryessa on Sept. 27, 1969. Shepard died of her wounds two days later while Hartnell survived. In total, five deaths have been attributed to the Zodiac that occurred between December 1968 and October 1969 in Northern California.

Bates, 18, was killed in October 1966 and found dead with multiple stab wounds in an alleyway on the Riverside City College campus. In the letter, Kinkead said Bates left the college library and returned to her vehicle, which had been tampered with so it would not start.

She was stabbed "numerous times" in her chest, stabbed once in the back and her throat was cut, Kinkead wrote in the letter to his counterpart in Napa County. She was also beaten and choked, he said.

Cheri Jo Bates. A group of cold case investigators claim the Bates murder is linked to the Zodiac Killer deaths. (Riverside Police Department )

"There are numerous similarities in your homicide and our Inv. 352-481 [Bates case number]," he wrote. "I thought you should be aware that we are working a similar-type homicide investigation."

After the Bates murder, Riverside police received a handwritten letter that led investigators to believe the killing may be linked to the Zodiac Killer. In 2016, investigators received an anonymous typed letter from someone who admitted to writing the earlier note and said it was a "sick joke."

During his investigation, Kinkead said they received a letter from someone stating facts about the Bates case only the killer would know.

Riverside Police Chief Lambert "Curly" Kinkead led the Riverside Police Department from 1965-1972. (City of Riverside)

"There is no doubt that the person who wrote the confession letter is our homicide suspect," he wrote.

Kinkead also noted the letter had numerous misspellings and punctuation errors, similar to letters written by the Zodiac Killer that were sent to law enforcement and the news media.

The Case Breakers believe they have identified the killer and said they have proof their suspect, an Air Force veteran who died in 2018, also killed Bates. Kinkead said footprints found near his crime scene were from a military-style boot.

Riverside police investigators do not believe the Bates killing and the Zodiac murders are related.

(The Case Breakers)

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"Our comment remains that our case is still unsolved and not related," police spokesman Ryan Railsback told Fox News.

In August, the department offered a $50,000 reward for information leading to the arrest or conviction of the killer.

Fox News has reached out to the Napa County Sheriff's Office.