Image copyright PA Image caption Melanie Hall was last seen alive in Bath in 1996

Detectives say they are "a step closer" to finding Melanie Hall's killer after new techniques uncovered DNA on an item found near her remains.

Speaking 20 years after she was last seen leaving a Bath nightclub, police said the discovery would help the investigation "significantly".

Miss Hall's remains were found at the side of a motorway slip-road in 2009.

Pat Hall said she would like to know "who it was" and why her daughter had been left "in such a ridiculous place".

Miss Hall, 25, who was a clerical worker at the Royal United Hospital in Bath, had been for a night out at Cadillacs nightclub when she was last seen on 9 June 1996.

Media playback is unsupported on your device Media caption Melanie's mother has been talking about the pain of discovering her daughter's body had been left "in such a public place"

A black bin liner containing her bones and skull was found by a workman clearing vegetation next to a slip-road at junction 14 of the M5, near Thornbury, South Gloucestershire, on 5 October 2009.

Nine people have been arrested in connection with the case since the investigation began but no-one has been charged.

'Someone knows'

Det Supt Andy Bevan said: "Through new techniques, we're in the process of developing a DNA profile.

"There's no doubt this brings us an important step closer to finding her killer."

Image copyright PA Image caption Miss Hall, who was a clerical worker at the Royal United Hospital in Bath, had been for a night out at Cadillacs nightclub when she was last seen

Image copyright PA Image caption Bones found near the side of the M5 motorway to the north of Bristol in 2009 were identified as Miss Hall's

Her mother Pat, from Bradford on Avon, said she would like to know "who it was and why" and why her daughter had been left "in such a ridiculous place, by the side of a motorway".

"It was just the fact that she had been found and left in such a public place with no dignity," Mrs Hall said.

"At least that allowed us to do that very last thing that a lot of us do for our loved ones, to actually be able to say goodbye in a dignified way."

Image copyright PA Image caption The 25-year-old went missing in 1996 wearing clothes and shoes similar to the ones pictured

Ms Hall's father Steve said they had realised within days that she was "probably dead or in serious trouble".

"Our lives have been totally altered and they can't be put back together completely," Mr Hall said.

"We're saying once again, someone out there knows something, someone could come forward with information which could solve this crime.

"I believe there are a number of people out there who probably know what happened to Melanie and the people involved and, for whatever reason, they've seen fit not to come forward."

Melanie Hall timeline

Media playback is unsupported on your device Media caption The unsolved murder of Melanie Hall

9 June 1996 - Melanie Hall is last seen at Cadillacs nightclub in Bath and a missing person inquiry is launched the next day

- Melanie Hall is last seen at Cadillacs nightclub in Bath and a missing person inquiry is launched the next day 13 March 2003 - Police search several sites in the Bath area following the arrest of two men in connection with the case. Months later the men are told they face no charges

- Police search several sites in the Bath area following the arrest of two men in connection with the case. Months later the men are told they face no charges 7 October 2009 - Bones found near the side of the M5 motorway to the north of Bristol are identified as Miss Hall's remains

Bones found near the side of the M5 motorway to the north of Bristol are identified as Miss Hall's remains 11 December 2009 - The funeral of Miss Hall takes place in Bath - 13 years after she went missing

- The funeral of Miss Hall takes place in Bath - 13 years after she went missing 25 November 2013 - A man is arrested on suspicion of her murder

- A man is arrested on suspicion of her murder 28 November 2014 - The Crown Prosecution Service says there is insufficient evidence to charge the man