An investigation has been launched into injuries caused by a police dog at an illegal rave.
A young woman at the event in Yate near Bristol claims to have sustained "life-changing injuries" to her leg.
Avon and Somerset Police has referred itself to the Independent Office for Police Conduct (IOPC).
At the time, the force said officers were pelted with missiles when they moved in to disperse the crowd.
In an interview with the Independent newspaper, 28 year-old Jessica Mae Andrew said the dog attacked as police closed down the event on 31 October.
She says her injuries included a broken bone and she needed skin and muscle grafts along with reconstructive surgery.
In a statement, the IOPC said: "We received a referral from Avon and Somerset Police after a member of the public sustained a dog bite injury in Yate.
"After careful consideration, we decided the matter was suitable for local investigation by the force.
"The IOPC will be provided with a copy of the force's final report so will retain some oversight of this matter."
An Avon and Somerset Police spokesman said: "The process is ongoing and will include reviewing body-worn camera footage.
"Our final report will be provided to the IOPC."
Some police officers who went to break up the rave suffered minor injuries after having missiles thrown at them.
Avon and Somerset Chief Constable Andy Marsh said those running the event had acted "criminally and disgracefully".
"It is hard to adequately explain how reckless it was to organise an unlicensed music event during the midst of a pandemic that has claimed so many lives."