Police have arrested nine people after an unlicensed rave in Norwich in the early hours of Sunday.
Norfolk Police were called to an empty industrial unit off Hurricane Way at about 0200 BST.
They found nearly 40 vehicles outside and 300 people attending the rave but called for back-up when they were met with abuse and violence.
One officer suffered a broken hand as arrests were made for violent disorder and drug possession.
Health and safety
Police had asked people to leave the building and all but 70 did so.
A spokesman for Norfolk Police said: "One of the concerns was for the safety of those attending the rave so liaison was made with health and safety and Norfolk Fire Service.
"When officers approached the building they were greeted with abuse and violence with one officer sustaining a broken hand for which he was taken to hospital.
"Another officer was injured but returned to duty after treatment.
"Additional Officers from other parts of the county were called in to assist."