Already reeling from two straight defeats, the Broncos were plunged into further drama on Sunday night when footage showed the pair engaged in a tussle.

Haas can be heard calling Kelly a f***ing c***, while also holding his hand to his throat and appearing to deliver a left-handed punch to Kelly's head.

The big-money Broncos prop also appears to shove the playmaker's face with his right hand, while slurred voices can be heard.

It is unclear when the video was taken, with Kelly not appearing to show signs of the foot injury he suffered in Saturday's loss to the Warriors.

"The matter has been referred to the NRL Integrity Unit and the club will investigate the matter further," a Broncos spokesman said.

The 22-year-old was last year handed a good behaviour bond over an altercation with police in Tweed Heads, where he was accused of intimidating a female officer.

It came after the NSW State of Origin prop was also suspended for four games at the start of 2019 for failing to cooperate with an NRL integrity unit investigation.

The incident is also not the first clash between current Broncos players after Jordan Riki and Tom Flegler were engaged in bust-up at the end of last season.