"Straight away you could tell Nielsen shouldn't be let into the club," a witness told Fairfax Media. "He'd had enough to drink but was walking around the club like he owned the joint and was spitting on the dance floor."

Suspended: Sharks five-eighth Ben Barba, who is serving a two-match ban, was at the nightspot where Dane Nielsen is alleged to have engaged in anti-social behaviour. Credit:Getty Images

While players from St George Illawarra and Cronulla were at the club, it is believed no other players are under NRL investigation. The witness said Nielsen then became involved in a heated exchange with Cronulla's Ben Barba.

"[Nielsen] was being a pest more than anything around Barba," the witness said. "Barba bought a couple of drinks for the players and Nielsen was trying to grab them off him, he has then grabbed them and threw them back over the bar. [Nielsen] was asked to leave. All the Cronulla boys and Saints boys left before they realised Dane was still in the club. He was trying to buy drinks but was denied. They went across the road and what I saw was Nielsen being a pest and he tried to grab Barba. Barba hit the deck and looked to have hurt his knee or shoulder. He was quite angry. The other players [tried to get in between them]. [Barba] pushed everyone off him and walked off."

The NRL is aware of an incident involving Nielsen. "The Dragons are investigating the incident and have advised the integrity unit," an NRL spokesman said. "As in all these cases the clubs conduct the inquires and the integrity unit only becomes involved if the penalty is deemed insufficient."