A group of around 80 youths were found gathering at a rugby club before leaving behind a "large amount of rubbish".
South Wales Police received reports that a large group of youths were at Trebanos Rugby Club in Pontardawe on Monday evening.
A tweet shared by officers at 7.21pm on June 1 said: "PCSOs Griffiths and Bayliss have been called to a report of a large gathering of youths at #TrebanosRFC.
"Approx 80 youths have been moved on from the location and alcohol confiscated, a large amount of rubbish has been left at the location."
It comes as officers from South Wales Police were also called to the former quarry near Crown Road, in Kenfig Hill on Saturday where a group of 100 children were found gathering.
And officers were called to Brombil Reservoir in Port Talbot at the weekend following reports of mass gatherings.
On May 31, South Wales Police received a number of reports of groups of young people involved in anti-social behaviour.
A statement released by the force said: "We’re urging parents to check where their children are.
"These reports include jumping into water from a height – known as tombstoning – and underage drinking.
"Not only are these potentially dangerous, but some are illegal. They are also a breach of Welsh Government restrictions, for which parents could be liable.
"We know the last couple of months have been tough, but we’d ask you to consider the impact anti-social behaviour may have on other people, on our health service, or on efforts to defeat this virus.
"We are continuing to patrol our communities but cannot do this alone."
Key changes to lockdown rules in Wales started on Monday, June 1.
This means that people from two different households can arrange to meet in parks and gardens for the first time.
However, people in Wales are being asked to stay local, which has been advised as five miles from your home.
