Police investigating the murder of university graduate Melanie Hall who disappeared 20 years ago have DNA evidence from where her remains were found.
Miss Hall, a clerical worker at the Royal United Hospital in Bath, Somerset, vanished after a night out at Cadillacs nightclub in the city on June 9 1996.
She was last seen at 1.10am sitting on a stool on the edge of the dance floor at the nightclub in Walcot Street, Bath, which has since been renamed ClubXL.
A workman found her remains in vegetation next to the junction 14 northbound slipway of the M5 in Thornbury on October 5 2009.
The detective leading the inquiry into Miss Hall's murder, who will make a new appeal for information on BBC1's Crimewatch Roadshow, confirmed officers have DNA evidence.
It was discovered at the spot where her remains were found.
Crimestoppers is also reinstating a reward of up to £10,000 for information leading to the arrest and conviction of the person or people responsible for the murder.
Detective Superintendent Andy Bevan, of Avon and Somerset Police, said he believed the DNA evidence would help the investigation "significantly".
"Melanie's parents and sister have for the past 20 years been caught up in a living nightmare and my heart goes out to them," Mr Bevan said.
"The discovery of Melanie's remains in 2009 gave them some answers, but it's the unanswered questions that continue to haunt them.
"We're doing everything we can to find these answers for them - most importantly, who killed Melanie and why.
"For the first time I'm able to confirm publicly that we do have DNA evidence which was left on an item found at the scene where Melanie's remains were discovered.
"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.
"There's been a great deal of speculation about this case, including the names of suspects potentially linked to this murder.
"We don't have a prime suspect and we don't have any conclusive evidence to suggest Melanie's death is linked to any other murders or sexual offences committed in our force area, or elsewhere in the country.
"There are, however, numerous people of interest in this investigation and we're looking into whether they have any potential link to this horrific crime.
"I believe the DNA profile we're developing will assist these enquiries significantly."
Since the investigation began, officers have received 1,700 calls from the public about the case and completed 5,700 tasks or investigative actions.
A total of 1,600 statements have been taken, while there have been nine arrests. No-one has ever been charged.
The force is asking for sightings of Miss Hall after 1.10am on June 9 1996, including of the graduate leaving the nightclub.
Those who were in the nightclub that evening - when England drew 1-1 with Switzerland in the opening game of the football Euro 96 Championships - and have not yet spoken to police are asked to come forward.
Police are also appealing for any witnesses to suspicious activity or a vehicle parked on the northbound junction 14 slipway of the M5 from the early hours of June 9 1996 to contact them.
People who are concerned about a change in behaviour of friends or relatives, or anyone showing a particular interest in Miss Hall's death, are asked to get in touch with police.
Miss Hall's clothing and belongings have never been found and those with information about where they may be should contact Avon and Somerset police.
They include a pale silk dress with a round neck, black suede mule shoes with straps across the front and an open toe, a cream single-breasted long-sleeved jacket and a satchel-type handbag.
Her cosmetics and Midland cheque book and bank card have never been found, along with items of jewellery including a Next watch and silver drop earrings.
Mr Bevan said the recent conviction of Christopher Hampton, who admitted murdering Bath teenager Melanie Road in 1984, "justifies our belief that crimes can be solved no matter how long ago they were committed".
"Christopher Hampton was described as a normal family man. The killer of Melanie Hall could easily be someone who has moved on with their lives," Mr Bevan said.
"They may have a family and be someone who is respected in their career or local community. What they do have is a very dark and terrible secret, which they must fear will one day be revealed.
"With the advancements in DNA, combined with traditional policing methods, I fully believe we're getting closer to finding that crucial piece of information which will help us solve this case.
"On this significant anniversary, I'd ask the public to think of Melanie's family and cast their minds back to the key dates and locations which feature in this case and carefully consider whether they can help us.
"Over the years loyalties can change and relationships alter - if you have any suspicions about someone you think may be connected to Melanie's death, please do the right thing and call us with a name."
The Operation Denmark Incident Room can be contacted on 0117 952 9788, while Crimestoppers can be contacted anonymously on 0800 555 111.