Police asked all schools to send letters to parents of children in year nine or above asking them to check if their children had been approached by either Sophie Brookes or Danielle Barnes on the social networking site.
Both accounts have now been suspended by Facebook.
Parents were told that if their children had been approached, they should contact their individual school welfare officer.
But the letter has caused confusion, and alarmed parents have contacted the Northants Telegraph and have taken to social media themselves to ask further question why only children in year nine and above were affected and to ask for more details to be released by the authorities.
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One concerned dad said: “Sending letters out with vague details on is not going to calm the fears of parents. We monitor what our son does on social media and we know
Another parent said: “The kids are confused as well as the parents.”
A Northamptonshire Police spokesman said: “Northamptonshire Police are investigating Facebook accounts set up in the name of Danielle Barnes and Sophie Brookes.
“We have written to a number of schools in the north of the county where we believe there may have been links to these accounts and we will be contacting safeguarding leads at each one
“As part of the investigation advice, Northamptonshire Police is providing advice around online safety, in particular urging parents to ensure their child’s own Facebook account is set to private and not to accept friend requests unless they know that person.
“Individuals can spend time learning about a young person’s interests from their online profiles and then use this knowledge to help them build up trust.”
If anyone has accepted a friend request from either of these two accounts, they are urged to call Northamptonshire Police on 101, quoting incident 12/2/2016 number 169 02/12/2016 and a member of police staff will then call them back.
Officers said parents should look our for the following concerns from their teens:
• Distancing themselves from family and friends
• Spending large amounts of time on their electronic devices
• Looking visibly tired
• Receiving money or gifts
• Change in fashion/appearance
• Mood Swings
• Secretive behaviour and refusal to disclose social media passwords