Police hunting for eight-year-old Sarah Payne were today resuming a detailed search of the Sussex countryside.

Sarah's parents faced up to the possibility their missing daughter may not be found alive.

The focus of the inquiry team has switched to the more rural areas to the north of West Sussex.

Police are establishing a corridor along the A24, which runs north past Horsham and Crawley, from the Sussex coast towards the M25 and London.

Yesterday the team combed rolling farmland on the Sussex Downs about one mile north of Littlehampton.

Family liaison officer Detective Sergeant Sean Scott said all the possible outcomes had been discussed with Sarah's family.

He said: "One of those options is that Sarah may not be found well and safe.

"The family are realistic but still hold on to the hope that she is well and safe, as do the inquiry team."

He added: "They are a remarkable family who, despite the circumstances, remain very strong and very positive."

Police now say they are convinced Sarah has been abducted after search teams failed to find anything in the area where she disappeared after playing with her brothers and sister near her grandparents' house near Ferring.

Superintendent Phil Clarke, leading the search aspect of the operation, said he would be making house to house inquiries in rural areas to ask people with local knowledge of places where it might be easy to hide someone.

Assistant Chief Constable Nigel Yeo said today: "The door on other possibilities - misadventure, mishap-type possibilities - is ajar, it is not firmly closed.

"We are still carrying on some actions in respect of that.

"But by dint of having no other evidence, abduction must become a stronger possibility."

Det Supt Alan Ladley confirmed today that police are examining a number of white vans as part of the search for one that was seen in the lane where Sarah is now thought to have been abducted on July 1.

One of the vans which police forensic experts are examining was modified over the weekend of July 1 and 2.

It had its rear doors replaced and wooden interior panelling was removed.

Det Supt Ladley said: "This was a very unusual modification which may have taken place in the street or outside a lock up garage and we are anxious to hear from anyone who saw the work taking place."

Police are still trying to identify a man spotted with a girl answering Sarah's description at a service station in Knutsford, Cheshire, the morning after she vanished. Police issued an e-fit picture on Tuesday night of the man.

The Operation Maple team has received more than 10,000 calls from the public with information about Sarah's disappearance.