They say the cause of death is not immediately obvious - but they are treating it as murder.

Police guard the crime scene

Miss Hall, who was 17, disappeared last weekend a few hundred yards from her home in Trimley St Mary after returning from a night out at the Bandbox nightclub in Felixstowe.

A man walking his dog on Friday night discovered her naked body in a water-filled ditch near a farm track in Creeting St Peter near Stowmarket, Suffolk.

The BBC's Stephen Cape: "Officers are confident they will eventually catch the murderer"

A police spokesman said further tests were being carried out and the cause of death should be known within a week.

Clothing appeal

Detective Superintendent Roy Lambert, who is heading the investigation, said officers were especially keen to find the clothes she had been wearing.

Det Supt Roy Lambert: "This is now a murder inquiry"

"As Vicky was found naked one of the main lines of inquiry at the moment is to trace the clothes she was wearing when she went missing.

"I would appeal for anyone finding her black dress, brown jacket, sandals or purse to contact the police immediately."

Vicky's parents, Graham, 45 and Lorinda, 43, who also have a son Steven, 15, are said to be "inconsolable" at their home.

'Pure evil'

Last night police were out in force in Felixstowe questioning visitors to the Bandbox Nightclub - where revellers observed a minute's silence at midnight in tribute to the dead girl.

Earlier on Sunday villagers also gathered to pray for Vicky and her family.

Canon Kenneth Wakefield said the murder was "pure evil".

He added: "Today all of us are in great turmoil as we see things happen in our society which are pure evil and beyond belief.

"Who could think that a young girl could not walk safely from Felixstowe to Trimley - and yet it has happened.

"Our prayers are particularly with the Hall family and all of their close friends."

Police said the community had given them a "tremendous" response, and they had spoken to 550 people since the body was found.

A week before Vicky disappeared a 19-year-old woman was raped in an alley near the Bandbox.

On Saturday police took away a burnt-out car found about a mile from the spot where the body was discovered.

A police spokesman said checks were being made to see whether the vehicle could be linked to the murder investigation.

Earlier this week, police questioned a 21-year-old Ipswich man about Vicky's disappearance.

He was released on police bail without charge pending further inquiries.