Four schoolchildren have been arrested after significant allegations of bullying at a party in Braunton.
Parents of hundreds of Braunton Academy students have been sent letters by police warning them about the worrying trend of unsupervised parties at a field in the Lobb area.
Police say the parties, which have been advertised on Facebook under the name of "Chunderfest", attract underage drinkers and have resulted in "serious criminal allegations of a bullying nature".
North Devon Sector Inspector Roger Bartlett said the arrests came as a result of a party held on Saturday, April 13.
He said: "There have been several unsupervised parties in the Lobb area which are giving us cause for concern.
"As a result we have received serious allegations of a bullying nature.
"The incident is being treated as Actual Bodily Harm (ABH) at present.
"Four boys and one girl aged between 15 and 16 have been arrested in connection with the incident.
"No further action has been taken against one of the boys. The rest have been released on police bail.
"The allegations include the circulation of images on Facebook."
Insp Bartlett has written to the parents of children in years nine, ten and eleven at Braunton Academy warning them about these parties.
In the letter he says: "I am writing to you as a parent of a child at Braunton to express the genuine concerns that I have about the potential harm faced by any young person attending such parties.
"Despite the serious nature of the allegations that are being investigated we have information that further gatherings, at this and other locations, may be planned.
"If you know that your child is attending such a party, then I need to impress upon you the risks that your child may be facing both directly to their health through the excessive and unsupervised consumption of alcohol, but also indirectly through their increased vulnerability to potentially harmful behaviour from others created by their intoxication.
"My advice to you is to not allow your children to attend any gathering where you believe alcohol may be available without being sure that there is a fit and proper person supervising their welfare and alcohol intake.
"I do not want any parent to face a call from the police advising them that their child has been arrested, or worse has come to serious harm."
Insp Bartlett said he had conducted an assembly at the school and also spoken to the land owner in a robust manner.
Anyone with information is asked to call police on 101 quoting crime reference number CN/13/116.