Police believe girls are still alive

The Chapman family on holiday in Menorca

Police believe missing schoolgirls Holly Wells and Jessica Chapman are still alive and being held captive.

Detectives say expert advice from criminal psychologists, offender profilers and experienced police officers suggest an abductor is keeping them against their will.

The assessment came as "significant" leads emerged from an examination of Holly's computer, which the 10-year-olds used to surf the internet shortly before their disappearance.

Holly gave this card to her friend

At the same time Detective Superintendent David Hankins, of Cambridgeshire Police, made another appeal to anyone who may be holding the girls.

He spoke of the "sheer hell" both their families are going through.

New pictures have also been released, showing Jessica and her family on a recent holiday.

Holly and Jessica disappeared from near their homes in Soham, Cambridgeshire, on Sunday.

The latest reliable sighting of the pair was in the high street at 1920 BST, police said on Friday.

	:	Holly and Jessica
Maps showing focus of the investigation

DS Hankins told a news conference on Friday morning: "We're working on the experience from elsewhere and it's our belief that the two girls are still alive, being held captive somewhere."

Earlier, he said on BBC Radio 4's Today programme: "Specialists, including offender profilers, have advised us that the circumstances we face here in Cambridgeshire suggest a reasonable possibility they are still with someone who has abducted them."

Classmates pleaded: "Just give them back."

He told BBC News the police were creating a profile of likely suspects and said: "We're building up a picture which is starting to emerge."

He repeated a direct appeal to the potential abductor to think again about their actions and their conscience.

"You can see from these photos how happy this family are on holiday," he said.

"Don't let these photos become some of the last pictures the family has to remember Jessica by."

He added: "The two families are going through sheer hell."

Police have received more than 3,500 calls and their website had more than 70,000 hits.

The police know the girls were on the internet for about 30 minutes until 1735 BST.

Child safety on the net
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But officers have refused to say whether the girls were using a chatroom.

It has also emerged parents in the area were warned about strangers, just weeks before Holly and Jessica disappeared.

But clues emerging from CCTV pictures of the pair, released on Friday, have "run dry", officers admit.

The parents are 'bearing up', say police

Four potential witnesses seen in the footage of the two girls were traced by police, but detectives said they had offered no further lines of inquiry.

Friends of the girls appealed on Friday for their supposed abductor to return them.

Natalie Parr, 10, said: "It's a really horrible feeling. Just bring them back."

A Junior Superstars competition that the two girls were due to take part in this weekend has been cancelled.

And a reconstruction of the girls' last known movements will be prepared by police over the weekend.

Tests are being done on a white van seized on Wednesday from a caravan park in Wentworth, about 10 miles from Soham.

About 250 officers are still conducting a search of the village, which is expected to be extended to the surrounding countryside at the weekend.

Both girls, who were wearing Manchester United shirts, are white, about 4ft 6in tall and slim.

Jessica is tanned and has shoulder-length brown hair while Holly is fair and has blonde hair.

Anyone with information should call police on 01480 422982.