A pitched battle at a South Shore beach that involved bottles and helmets is under investigation by police.But the service said they could not confirm that a man who later went to the hospital’s emergency department with a stab wound to his arm had been involved in the brawl.A police spokesman said the injured man was interviewed, but refused to say how he was wounded.The fight, at Chaplin Bay, on South Shore, Warwick, which involved “a large group of men” happened at about 8.20pm on Wednesday.Police said most people who had been at the scene had left the beach by the time officers arrived.The spokesman said people left in the area declined to answer police questions.He added that officers maintained a higher than usual presence in the area after the incident.