Police have been called to Cardiff Bay to monitor the area after crowds gathered at Roald Dahl Plass on Saturday evening.
A Force Incident Manager from South Wales Police said it had been contacted and that they have officers in the area and are monitoring CCTV.
Pictures show some people drinking and police officers at the scene.
On June 26, police were called to break up a mass gathering in the same area involving hundreds of people. Local residents described "appalling" behaviour as people urinated against walls, cars parked on double yellow lines blocking Bute Crescent and car engines revved late into the night.
It was the second night in a row that this had happened. On the morning of June 26, local council staff had to clear up a large amount of rubbish left in the area from the night before.
Beer cans and bottles were strewn across the area. It also included nitrous oxide gas canisters commonly used as a recreational drug and refereed to as 'hippy crack'.
