By Paul Sims and Chris Brooke A predator on the Sex Offenders' Register killed a 17-year-old girl he met and groomed on Facebook after luring her to a secret meeting. The 32-year-old posed as a 16-year-old boy to befriend Ashleigh Hall on the social networking site. But within hours of their first meeting, the teenager was dead. The man is said to have bound and gagged her, and thrown her into the back of his car. Hours later he dumped her body in a ditch by a country lane. Last night he was being quizzed on suspicion of murder. At the police station he dramatically confessed: 'I've killed a girl', before leading them to the body. The killing raises serious questions over how effectively the known sex offender was being monitored. As a registered sex attacker he was required to inform police of any change of address. Checks carried out after his arrest, however, revealed he had moved from his registered home without notifying the authorities. Ashleigh, who was studying childcare at Darlington College, left her house at 7pm on Sunday, telling her mother she was going to stay at a friend's house and would be back the following afternoon. When she failed to return her mother repeatedly rang her mobile phone but there was no reply. On Monday evening at 5.40pm, traffic officers, alerted by their onboard computer, pulled over a Ford Mondeo being driven without any insurance on the A177 in County Durham. They arrested the driver on suspicion of motoring offences and took him to Middlesbrough police station. He was then booked in and taken to a cell. He told a custody officer: 'I want to tell you something, I want to speak to a detective.' The man then told officers that he had killed a girl. He claimed she had suffocated after he gagged her and insisted it was an accident. He offered to take them to the lane where he had dumped her body in Sedgefield He took them to the place where he said he had flung the body on a road known locally as lovers' lane. Ashleigh's body was discovered at around 10.30pm. After the body was found the man was taken to Darlington Police station where he underwent a medical examination, though detectives would not reveal if he had sustained any injuries either before, during or after the girl's death. Nor would they confirm how the girl had died or whether she had been sexually assaulted. The man gave detectives two names - one believed to be an alias - but officers are convinced they know who he is and have taken his fingerprints to establish his identity beyond doubt. The man, who had a shaved head, is believed to have links with Merseyside and Stockton-on-Tees. Police sources said he had previous convictions for sex attacks on young women and was a registered sex offender. It is not known, however, if he was being monitored by Multi Agency Public Protection Arrangements, an agency set up to keep a close eye on dangerous sex offenders. The girl's body was taken to Darlington Memorial Hospital where a post-mortem examination was being carried out by a Home Office pathologist. Forensic officers yesterday continued to examine the scene just yards from a Little Chef restaurant and Travelodge hotel. Detective Chief Inspector Paul Harker said the body of the girl, who had not been reported missing, could have been there for up to 24 hours. The car was also undergoing a forensic examination. DCI Harker said that the girl's family had since looked on her computer and discovered conversations with an unknown man. It is not known if that is the same man police now have in custody. Friends said she had met the man online and that he had claimed to be 16. Danny Fisher, 17, from Darlington, who went to college with Ashleigh, said: 'She was always really popular. 'I heard that she had been talking with a man on Facebook. He told her he was 16, but obviously it looks like that was a lie.' Ashleigh, who had four sisters, left Hurworth School in Darlington last year after completing her GCSEs. The school's headmaster Eamonn Farrar said: 'I'm absolutely stunned. I heard it on the news and thought it couldn't be our Ashleigh, but then the news came through to my colleague. I just can't believe it. 'We will try to remember Ashleigh not in terms of her passing, but as a student at Hurworth, and one we were all fond of. On the dangers of forging relationships on the internet, he added: 'This shouldn't happen to anybody. 'We need to have a look at it and find out why it's happened and try to make sure that no one else becomes a victim of this kind of incident.' The man was driving a dark blue Ford Mondeo, registration S148 JNK. Officers are appealing for help to establish its movements from 7pm on Sunday evening until the arrest at 5.40pm on Monday. Source: www.dailymail.co.uk