Police were also seen speaking with United staff post-match.

A late send-off of Roar goalkeeper Michael Theo, and a subsequent winning penalty by the Reds, sent tensions soaring.

An altercation between two assistant coaches – Ross Aloisi of Roar and Jacobo Ramallo of Adelaide - was described by Fox Sports as a "physical confrontation".

Aloisi was later seen speaking to the Match Commissioner after the final whistle.

SA Police released the following statement on Sunday night: "Police have not received a report from any officials from either club regarding an alleged assault."

Roar confirmed that FFA was looking into the matter: "Brisbane Roar Football Club are aware of an investigation by Football Federation Australia (FFA) into an incident that occurred after full-time in the club’s Hyundai A-League match against Adelaide United at Coopers Stadium on Sunday.

"BRFC intends to fully cooperate with the FFA.

"Brisbane Roar FC will not make further comment until speaking to those involved and a thorough investigation is concluded."

Man lying on the ground in entrance to the tunnel

GALLERY: Match action from Coopers

MATCH REPORT: Adelaide snatch win after bizarre send-off

Fox Sports Daniel Garb reported after the match:  "Massive drama here at Coopers Stadium on and off the field.

"It started with a last minute penalty to give Adelaide the 2-1 win over Brisbane, And then, tempers boiled over in the tunnel after the game.

"We can tell you the breaking news is that there has been an altercation between two of the assistant coaches..."

Meanwhile, Roar's first team coach, John Aloisi. looked for Guillermo Amor immediately after the match, but the Reds coach had already left the pitch.

The stoppage time penalty brought a controversial end to the game. Michael Theo collected the ball and was apparently fouled by Dylan McGowan before lashing out with his elbow.

The goalkeeper was the sent off and, with all their subs used, Thomas Kristensen went into goals, Sergio Cirio converting from the spot to give Adelaide the win at the death.