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.