POLICE have arrested a man on the suspicion of kidnapping Sian O'Callaghan.

At a news conference at Gablecross Police Station shortly before 1pm, Chief Superintendent Steve Hedley said a man has been arrested on the suspicion of kidnapping Sian.

He said they are still hopeful she is alive and they are doing all they can to find her.

They are now directing all the enquires into this but said it was a significant development.

Chief Superintendent Steve Hedley said: "A short time ago a man was arrested on suspicion of the kidnap of Sian O'Callaghan and is on route to a police custody centre.

"Sian's family have been informed.

"Further information will be released in due course but it is not appropriate for me to make any further comment at this time."

Earlier, police towed away a green taxi matching the description of the car they are looking for in connection with their hunt for Sian O'Callaghan.

The vehicle was loaded onto the back of a lorry and taken away after police swooped on the car park of ASDA Wal*Mart at the Orbital shopping centre in North Swindon.

The taxi, a green Toyota Avensis estate, was seen between Swindon and the Savernake Forest, near Marlborough, Wiltshire, shortly after Miss O'Callaghan was last seen early on Saturday morning.

Detective Superintendent Steve Fulcher, who is leading the inquiry, said: "I am urgently appealing for any witness sightings of a green Toyota Avensis estate with taxi markings seen between 3am, 4am and 12pm to 9pm on Saturday 19th March 2011 between Swindon and Savernake."

Anyone who saw the vehicle or who has information is asked to contact police immediately on 0845 408 7000 or Crimestoppers 0800 555 111 where details may be left anonymously.