As many as 3,000 people are thought to have travelled to an illegal rave in Wales today, despite new rules to crack down on mass gatherings in Britain due to the coronavirus pandemic.
Officers are at the scene in Banwen, Neath Port Talbot and South Wales Police have condemned the "totally unacceptable" event.
It comes after police in Norfolk, England worked to shut down an all-night unlicensed music event in a forest attended by more than 500 people.
Norfolk Police described the organisation of a large gathering in Thetford Forest, which began late last night, as "extremely disappointing".