LONDON, Aug 16 (AFP) - Police investigating the disappearance of English 10-year-olds Holly Wells and Jessica Chapman said no contact had been made with their suspected kidnapper after a deadline of midnight (2300 GMT) Thursday expired for him to call the officer leading the hunt.

Detective Superintendent David Beck sent out a televised appeal to any abductor -- or perhaps abductors -- to get in touch, using a hotline number that has been sent as a text message and voice mail to to Jessica's cellphone.

Under increasing pressure to solve the case, Beck had said: "I appeal to you to work with me to stop this getting any worse than it is.

"You do have a way out... You have an opportunity to speak to me. This is the time to use it."

Holly and Jessica disappeared 12 days ago, on Sunday, August 4, in their home town of Soham, northeast of the English university city of Cambridge, in a case that has dominated the news in Britain.

More than 400 police have been put on the case, vast swathes of countryside searched, and more than 400 house inquiries carried out in one of the biggest missing persons' cases ever in Britain.

Detective Chief Inspector Andy Hebb said: "If someone is holding the girls it is possible that they don't have access to Jessica's phone and therefore could not access the message left by Mr Beck."

He added: "We don't know with certainty that Holly and Jessica have been abducted and therefore are not unduly anxious about the fact that no call has been received.

"We will reconsider our options later today once we have taken expert advice about how this line of inquiry may be progressed.

"Our optimism about finding Jessica and Holly alive remains as strong as it was on day one of this inquiry.

"The fact that we have not received a phone call from a possible abductor has not changed that, nor has our commitment or determination to find both girls and return them to their families."

On Thursday Hebb said there were "many, many positive lines of inquiry" apart from the phone appeal. He refused to elaborate for what he said were operational reasons. - Nampa-AFP