Detectives have said they are confident they will catch the killer of Melanie Hall, the NHS worker who vanished from Bath 23 years ago, after traces of DNA were found on rope used to conceal her body.

Hall, 25, was last seen alive in Cadillacs nightclub in the city in the early hours of 9 June 1996. Her remains were found 10 years ago to the day, wrapped in bin liners secured with a rope and hidden in undergrowth next to a motorway slip road.

Detectives have now revealed that a partial DNA profile has been obtained from the rope, which could be that of the killer or of someone who disposed of the body.

Speaking at the spot where the body was found, DCI James Riccio, of Avon and Somerset police, said: “We’re confirming the DNA traces were found on a blue polypropylene rope which was wrapped around thin black bin liners which had contained her body.”

Riccio said the rope was not a single length but four separate pieces knotted together. He said the rope was dirty and included seven knots – three joining the lengths together and four extra ones. The detective said the number of knots was “intriguing” but he could not explain why there were seven.

A replica of the rope that secured bin liners wrapped around Melanie Hall’s remains. Photograph: Avon and Somerset police/PA

“It’s commercially manufactured rope and commonly used on building sites and for drawing electrical cable through trunking,” he said.

When asked whether the DNA traces could be those of Hall’s killer, Riccio replied: “It is possible.” He described the DNA investigation as being “in its embryonic stages”, but said advances in technology were being developed. “We’re confident that, with corroborative evidence, that will lead to a charge,” he said. “I’m confident we’ll get justice.”

Police believe the area where Hall’s remains were discovered is another vital clue.

Detectives suspect the body was left in haste in the undergrowth close to the junction 14 northbound slip road of the M5 either on the morning of 9 June or within a few days of that date. The spot is 30 miles north-west of Bath.

It is likely the person would have then driven on to the northbound M5 motorway and either on to the next junction, or perhaps have turned off at Michaelwood services and left it via a small road within the services area to head back in a southerly direction.

“It’s quite an odd place to dump a body,” Riccio said, adding that it was “highly likely” that the person who left Hall’s body in the undergrowth was familiar with the area.

He also emphasised that the person or people who hid the body might not be the killer.

Police officers sift and check soil at the site where Melanie Hall’s remains were found. Photograph: Ben Birchall/PA

There have been 11 arrests during the investigation into Hall’s murder, but no one has ever been charged. Riccio said work was still being carried out in relation to some of these people.

Appealing directly to an accomplice or accomplices, he said: “You’ve been living with a dark secret for years but your guilt and fear is nothing compared to the enduring pain felt by Melanie’s family. I want to be clear: our primary focus is on identifying the person or persons who killed Melanie.”

In the past, the convicted double killer Christopher Halliwell – whose story is currently being told in the ITV drama A Confession starring Martin Freeman – has been linked to Hall’s murder, but Avon and Somerset police have insisted there is no evidence linking him to it.

The victim’s father, Steve Hall, said he and his family remained “eternally optimistic” that the mystery of his daughter’s death would be solved.

He said: “In our family we will forever grieve for and miss our lovely daughter. A young woman whose life stretched before her until that fateful night in June 1996, when that life was so cruelly snatched from her.

“She will never fulfil her life’s ambitions, never marry, never have children and my wife and I will never have another grandchild.”

Hall’s parents have reinstated a £50,000 reward for information provided to the police that leads to the arrest and conviction of the person or people responsible for the murder. The independent charity Crimestoppers is also reinstating a reward of up to £10,000.

Hall said: “Her mother’s lasting memory of her youngest daughter is the day she viewed a battered skull and a few broken bones in the coroner’s office.”

Anyone with information should call the Operation Denmark incident room on 01278 648934 or submit information online.