Charred bones found on a Melbourne beach most likely belong to a petite woman more than 20 years old and the detectives assigned to the baffling case are asking for help to unravel the mystery of her identity.

Despite 18 months of forensic tests and scanning missing person profiles, Victoria Police have no clue who the person is or how they died.

The unusual case unfolded after a jawbone was found in the foreshore rock pools at Ricketts Point in Beaumaris on 11 January last year by Parks Victoria staff.

When forensic tests showed it was human, police returned to the pools and found more than 400 other bone fragments, all belonging to the same person.

The bones make up about a third of a skeleton, most likely a petite female, older than 20 years, and between 155cm and 160cm tall.

The lower jaw also has back teeth missing on each side, pre-death.

Police have scanned missing person profiles in Victoria and interstate with no luck.

They also made inquiries at Melbourne’s major crematoriums, which say they never release all the bones of a deceased to a family.

The bones are severely burnt and “it’s probably more likely than not that it is suspicious”, missing persons squad detective sergeant Maurie Ryan said on Thursday.

“It’s extremely frustrating and difficult for us. We still don’t, after this time, have any idea who this person is.”

Detectives believe the bones were only recently placed in the rock pools, given their location and changing tides.

It’s believed they were discarded there some time in early January 2018 or late December 2017.

The remaining 70% of the skeleton likely washed out with the tides, Ryan said.

Anyone aware of someone who disappeared during that period is urged to contact police.

Investigators also want to talk to anyone who saw suspicious or unusual behaviour or someone discarding items at the beach during that time.

“Was she left here by loved ones? Was she murdered? We just don’t know,” Ryan said.

“Some of the best forensic scientists in Victoria have examined these bones, and while they have been able to provide us with some information, it alone hasn’t been enough to solve the case.

“There is definitely a story behind these bones and it’s one we want to know – and there will definitely be someone out there who can tell it to us.”