Three teenage girls have been arrested and bailed on suspicion of assault following a video being posted online.
Two 14-year-olds and a 15-year-old were arrested after police made inquiries into the footage of two girls fighting in Blackburn town centre.
The video, which was posted on Facebook, showed one girl pulling the hair of another, kicking her and punching her in the face.
Inspector Ilyas Mohmed said: “We do not tolerate this kind of behaviour and we will take positive action against anyone who commits these kind of vile attacks.
“I would call on the community not to take matters into their own hands and let us deal with the incident.”
In a statement on the social networking site yesterday, Blackburn police said: “Blackburn town centre police have been made aware of a video having been posted on Facebook which shows a teenage girl being seriously assaulted by another teenage girl.
“This incident is believed to have taken place this afternoon close to the grounds of Blackburn college.
“We would reassure people that an investigation is underway and would ask anybody that has witnessed this assault to contact police on 101 quoting log 1021.”
A police spokeswoman said that inquires were still ongoing and that officers were looking to talk to the other people involved in the video.