Image source, Getty ImagesImage caption, San Francisco police published sketches an unnamed suspect in 1969

Officials in California have said the man identified by private investigators as the so-called Zodiac Killer is not currently a suspect in the case.

The serial killer murdered at least five people, terrorising the San Francisco Bay area in the late 1960s. He has never been identified.

On Wednesday, the Case Breakers – a group of cold case specialists – named a man who died in 2018 as the killer.

But the FBI and local police have pushed back against the allegations.

Police and newspaper reporters reportedly receive hundreds of tips each year on possible suspects in the decades old mystery.

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No ordinary tipsters, the Case Breakers are a team of over 40 volunteers from law enforcement, military, legal and academic backgrounds.

They say new physical and forensic evidence all connect a man named Gary Francis Poste to the infamous slayings.

The group – whose website boasts fresh leads on several high-profile cases – says Poste is also "a very strong suspect" in the death of a teen girl hundreds of miles away, a case never linked to the Zodiac.

Among the new claims are similarities between Poste and a 1969 police sketch of the Zodiac, and in particular, the "irrefutable" likeness of scars on their foreheads.

The Case Breakers also say deciphered letters from the Zodiac contain anagrams of Poste's name.

In its Wednesday press release, the unofficial task force said it had "signed up eyewitnesses, filed court affidavits, and secured decades of pictures from Poste's former darkroom" over the course of a 10-year state-wide examination, to back up the allegations.

But law enforcement agencies have batted down their claims.

Local police in San Francisco and Riverside also dismissed the group's "circumstantial evidence".

The last major break in the Zodiac case came late last year, when the FBI confirmed independent code-breakers had cracked one of several taunting messages sent to newspapers during the killing spree.

The decrypted message, sent to the San Francisco Chronicle, provided no new evidence of the killer's identity but contained the message: "I hope you are having lots of fun in trying to catch me."

David Oranchak, the Virginia web designer who helped crack the cipher, told the Chronicle on Wednesday that it was "unlikely" the killer included his name as an anagram in the letters.

The Zodiac Killer gained notoriety with his letters to the newspapers and to police, in which he claimed to have murdered as many as 37 people. Investigators have worked on the basis of seven victims in total, five of them homicides.

The murders inspired two films – 2007's Zodiac, featuring Robert Downey Jr and Jake Gyllenhaal, and Dirty Harry in 1971 starring Clint Eastwood as a tough San Francisco detective.