A man remains in police custody today suspected of killing nightclubber Sian O'Callaghan as police continue the search for a second murder victim.

Painstaking new searches have been launched after detectives said that a man suspected of killing Miss O'Callaghan gave them new information on the whereabouts of another body.

The fresh forensic effort was sparked as the suspect reportedly told police where to find the remains of a second missing person.

Detectives believe searches on the Oxfordshire-Gloucestershire boundary will lead them to Wiltshire's "one outstanding" missing person.

Det Supt Steve Fulcher said the person had gone missing "several years ago" as search teams sifted land at Baxter's Farm, between the villages of Eastleach and Filkins.

Police refused to comment on speculation the remains they were looking for could belong to 39-year-old Tina Pryer. The mother-of-three was last seen getting in a taxi in Trowbridge in April 2001.

The suspect, named locally as taxi driver Christopher Halliwell, appeared before Swindon magistrates on Friday afternoon as officers were granted another 24 hours to quiz him.

Mr Fulcher, who is leading the inquiry for Wiltshire Police, said he had been personally taken by the suspect to the location where Miss O'Callaghan's body was found and where the search had begun for a second victim.

Officers were using mechanical diggers to excavate the corner of a field in their hunt for a second body.

Part of a dry stone wall was removed and two trenches were excavated, where officers in protective clothing were on their hands and knees in the mud.

Officers refused to discuss reports they had been in contact with police in Somerset regarding the 1996 disappearance of Melanie Hall. Avon and Somerset police also had no comment.

Police said they would not speculate on the identity of the person they were looking for.