Facebook has urged internet users not to meet strangers they have only had contact with online after a teenage girl was kidnapped, raped and murdered by a convicted sex offender she met on a social networking site.
The warning came after convicted rapist Peter Chapman, 33 - who was also suspected of other attacks - met 17-year-old Ashleigh Hall online.
Chapman, who admitted kidnap, rape and murder, was on Monday jailed for life and told he would serve at least 35 years.
Ashleigh's mother, Andrea Hall, also warned of the dangers of social networking sites and questioned why Chapman was free to attack her daughter.
In a statement, Facebook said it was "deeply saddened" by Ashleigh's death. The statement urged people not to meet anyone they have only had contact with online unless they are certain they know who they are, "as there are unscrupulous people in the world with malevolent agendas".
Speaking after the sentencing at Teesside Crown Court, Mrs Hall said she had been powerless to stop Ashleigh going out that fateful night.
"Them sort of people should be tagged and they should be kept an eye on all the time," she said. "I blame them for letting them out. He shouldn't have been let out."
Mrs Hall, who was comforted by her family and friends, said she was powerless to stop Ashleigh going out.
"What could I have done?" she asked. "She was 17. You don't stop your kids from going out. You tell them to be careful. He was a nice-looking boy. I couldn't have stopped it and I wouldn't have stopped it.
"The message is for people just to be careful. Please just be careful. Make sure you please do tell somebody if you are going to meet a person. That is the message, don't go on your own."