Police have launched an investigation into allegations of grooming affecting youngsters at a West Norfolk school.
A letter has been issued to parents of children at Eastgate Academy after two of its pupils were targeted via a social networking app.
The pupils concerned, who were girls, were using the social media site Musically.
Chief Inspector Ed Brown, said: “Norfolk Police are aware of this incident and are currently investigating.
“The Safe Guarding Children Online Team (SCOLT) are leading on this and the child’s phone has been seized as part of that investigation.
“The constabulary are committed to dealing with grooming and any other online abuse. We work closely with schools to raise awareness about these kind of issues.
“Parents are encouraged to talk with their children about internet safety but we also want to get to a situation where children feel comfortable talking to their parents about any concerns they have online.”
Eastgate Academy principal Linda Hothersall said: “Safeguarding is a priority within the Academy and online safety is an integral part of our curriculum.
“We felt that it was important that all parents were made aware of the potential risks in using this app.“
On Tuesday, the Academy issued the following letter to parents and guardians of children.
Entitled safeguarding, it read: “We have had an incident in school today where two children in our school have been groomed on line by two men.
“The children have been using an app called Musically. It’s a social media site known to our children and they use it to contact each other and ‘add new friends.’
“There have been two incidents, one over the weekend and another one last night.
“A man who says he’s 22 has propositioned the girls, calling them sexy and asking them to do sexual things to him.”
It also added that a man, who befriended the children beforehand through the Musically app, had asked the children to go on a live chat where he exposed himself to them.
The letter ended by saying: “We have asked all children to talk to their parents if they use this app and have asked them to delete it.
“We are asking for your support with this to help us to keep our children safe.”