Canterbury Bulldogs chief executive Raelene Castle confirmed a glass bottle was thrown in the vicinity of the Canberra Raiders bench during their NRL meeting on Monday.
The incident occurred during the Raiders' 22-8 victory at the Belmore Sports Ground, home of the Bulldogs.
According to reports, the bottle narrowly missed Canberra players on exercise bikes on the sidelines, but Canterbury officials are confident they are aware of who the culprit is.
"I believe it was [a glass bottle]. You can't get glass in here unless you have snuck it in," said Castle.
"We have identified an individual and our fans also helped us identify who the person is.
"We have dealt with it really quickly and the person was ejected. It's not acceptable - absolutely not acceptable. We'll be doing all we can to make sure that we communicate with our fans that that behaviour is not acceptable.
"We believe we know who the person is."
Raiders coach Ricky Stuart condemned the action of the supporter but was impressed with how the situation was handled.
"The Bulldogs have dealt with it very professionally and very well. Canterbury is a great club and they jumped on it quickly and we don't want those types of supporters in our game," he said.