Less than three weeks out from the NRL season-opener in Las Vegas, footage appeared on social media on Monday of Broncos captain Reynolds and lock Carrigan wrestling.
The Broncos are investigating the incident, which happened after the club's fan day on Sunday.
In the footage, a female at the scene can be heard calling out, "Adam ... Pat ... stop".
"The Broncos are looking into an incident involving some of its playing group in Brisbane City last night," the club said in a statement, adding they had kept the NRL's integrity unit updated on the situation.
"The club was made aware of the incident last night and has been speaking to players across the course of the day to clarify details of what occurred."
Reynolds and Carrigan are senior leaders at the club and two of the vital cogs in the Broncos' quest to go one better than last year, when they suffered grand final heartbreak in a 26-24 loss to Penrith.
The pair are also expected to be among the key faces of the sport in its push into Las Vegas and the USA, with Brisbane to fly out next week for their March 2 season-opener against the Sydney Roosters at Allegiant Stadium.
"The NRL integrity unit is aware of the matter and is liaising with the club," an NRL spokesman said.
The incident is the second scuffle between Broncos players to go public in the past two years, after Payne Haas and Albert Kelly were each suspended for one game following a 2022 incident.
Sunday was a massive day on the club's calender, with thousands of fans turning out to meet the squad, including Reynolds and Carrigan.
Players went out afterwards for a social gathering.
Pat Carrigan praised the turnout at a Brisbane fan day ahead of Sunday evening's incident. (Pat Hoelscher/AAP PHOTOS)
Carrigan had spoken at the Broncos fan day praising the turnout.
"It just shows people believe in us. We have a job to do and that is play good footy for these fans," he said.
"They have been there since day dot. We respect that and are grateful for their unwavering support."
Carrigan said it was vital Brisbane got off to a winning start in round one against the Roosters in the unfamiliar surroundings of Las Vegas.
"It is all the unknown," he said.
"We are going to the big smoke in Las Vegas to play a game of NRL. It is pretty cool but Kevvie (Walters) is good at keeping us grounded.
"We have got a big year ahead of us and it is a good opportunity to hit the ground running."
