The Canberra Raiders are in damage control after suggestions a star player has been involved in an incident he could regret "for the rest of his life".

Raiders' chief executive Don Furner would not name the NRL player allegedly involved or detail the incident but said an investigation was under way.

"If he did it, it is something he will live with for the rest of his life," Furner told a media conference.

The nature of the investigation is not clear but it is understood the NRL is involved, various websites reported.

The incident reportedly happened during the Raiders' Mad Monday celebrations following their finals loss to Wests Tigers.

A photo showing the incident was reportedly posted on the internet on Monday before being taken down by the Melbourne radio station that had put it online.

The action was too late with the image being re-posted through Twitter.

"We don't know whether it's authentic but I am as appalled as everyone else," Furner said.

"If he did do it, I don't know why he would do it."

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