Sniffer dogs were yesterday (Thursday) taken to the Malmesbury building site that police now say is of "significant interest" in the hunt for missing Purton woman Amanda Edwards.

As the dogs were searching the former Knoll House Hotel site, detectives were becoming increasingly concerned for the 21-year-old's welfare.

Detectives last night released the man they had been questioning on suspicion of kidnapping Amanda. The 42-year-old had been arrested on Monday evening at his Swindon home.

When the initial 36-hour questioning period elapsed, a further warrant was obtained which gave police until early yesterday morning.

They then obtained a warrant for a further 15 hours' questioning, which expired at midnight last night.

The suspect was then released without charge. The man, who police say is not her boyfriend or a family member, is an acquaintance of the nursery assistant.

Detectives are now also looking for a white Ford Transit van which might play a key role in the investigation.

Det Chief Supt Paul Howlett, head of Wiltshire CID and the man leading the inquiry, said: "We continue to search that building site and we are very keen to hear from anyone who might have seen unusual activity at this location after last Thursday and then over the Bank Holiday weekend.

"In particular we are keen to hear about any sightings of a white Ford Transit van that has lettering on the side panels."

And, on the one-week anniversary of Amanda's disappearance, police were encouraged by CCTV footage taken from Wootton Bassett which they believe shows Amanda driving towards Swindon at 11.55am last Thursday.

Prior to this, they had not known where she had been after dropping off her 19-year-old boyfriend David Board at his home in Bremhill, Calne, at 11.30am.

The vehicle appears to be driven by a lone female and fits the description of Amanda's car, a racing green Rover Metro with distinctive red windscreen wipers.

Det Chief Supt Howlett said: "If this proves to be Amanda's car and it is her driving then we have made significant headway. Wootton Bassett is only about five miles away from this car park. This helps us to have some idea of what time she might have arrived at the West Swindon District Centre."

Amanda's car was found abandoned at Car Park C at the shopping centre at around 6.15pm later that day.

Yesterday, police flooded the centre, speaking to thousands of shoppers in the hope of uncovering fresh clues. Everyone who went into the centre was stopped and asked a series of questions.

Police had parked a car identical to Amanda's with her registration number plates at the exact spot where it was found last Thursday in the hope of jogging people's memories.

According to officers, members of the public had been helpful and had responded well, but it was too soon to tell if any new leads had been generated.

And, once again, Det Chief Supt Howlett made a plea for the public to further assist the police with their inquiries and "fill in the gaps" of the investigation.

Standing at the spot where Amanda's car was found, he said: "Many people would have driven past Amanda's car as it was parked here.

"Someone must have seen who was with Amanda's car when it arrived. Someone must have seen who left the car parked in this location. This is the information I desperately need.

"People are creatures of habit. I want to jog people's memories. I appeal to anyone who came shopping here last Thursday afternoon to think back and try to remember if they saw either Amanda's car or indeed who was with the car.

"Please do not make the assumption that the police will already be aware of information that you might have.

"The family are obviously very distressed. Just try to imagine what they are going through. If your child disappeared in this way, you would want as much help as possible."

Amanda is of mixed race, 5ft 6ins tall, very slim build with brown eyes and black hair cut in a short bob style. She was wearing a number of rings including an engagement ring. She was last seen wearing a dark blue Ellesse tracksuit top with a red stripe running down each arm and red piping and dark green trousers with a white A printed on the right hand side.

Anyone with information is asked to contact the incident room on 01380 735735 or Crimestoppers on 0800 555 111.