Detectives investigating the murder of a young hospital worker have released more clues as they try to identify her killer - six months after her bones were found dumped beside the M5.

Melanie Hall, 25, from Bradford Leigh, was last seen alive enjoying a night out in Bath, in 1996. Her remains were found last October near junction 14 of the M5 by a workman clearing vegetation.

Avon and Somerset Police said that they have still not established what happened to Miss Hall after she was last seen at Cadillacs nightclub, in Walcot Street, on June 9, 1996.

In a bid to jog witnesses' memories, detectives have released images of clothing "similar" to that worn by Miss Hall prior to her disappearance. They believe the killer may have kept one or some items as a trophy.

Detective Superintendent Mike Courtiour, leading the case, said: "The investigation team has continued to work tirelessly during the past six months, following up new information we have received and revisiting the previous investigations that followed Melanie's disappearance from Walcot Street, back in 1996.

"250 additional statements have been taken and 1,200 new tasks and investigative actions have been completed. The forensic work has been extensive and is still continuing today. Results of ongoing sensitive scientific tests are still not complete. However, at this moment, there is no forensic breakthrough.

"We have still not established what happened to Melanie after she was last seen in Cadillacs nightclub, just after 1am on Sunday 9th June 1996. Where did she go? Who was she with? What happened to her and then resulted in her body being dumped 30 miles away, wrapped in black bins bags and tied up with blue rope.

"On that evening, Melanie was wearing a distinctive blue silk dress with a round neck. She had on black suede mule shoes, with straps across the front and an open toe.

"We believe they were a size 5 or 6. She had a yellow/creamy coloured single-breasted long sleeved hip-length jacket. She was carrying a black satchel-type handbag with an 18 inch-long strap and a front flap opening. In her bag were some cosmetics and a Midland cheque book and bank card.

"She wore a Next watch with an expanding bracelet and had on silver drop earrings. None of her clothing or property I have described has been recovered or found.

Miss Hall, a psychology graduate, had been on a night out with friends and her boyfriend of three weeks, Dr Philip Karlbaum, who left the club "upset" after seeing her dancing with another man.

Miss Hall, who worked as a clerical officer in the orthopaedic department at the Royal United Hospital in Bath where she met Dr Karlbaum, was last seen sitting on a stool near the dancefloor shortly after 1am.

Thousands of nightclubbers and taxi drivers were interviewed in an investigation involving 60 officers and several searches of the River Avon, but no trace of Miss Hall was found.

That was until October last year, when her remains were discovered hidden under five plastic bags. A ring which had been in her family for generations was also found.