Cronulla Sharks prop Andrew Fifita has denied displaying a message on an armband during the NRL season calling for imprisoned friend Kieran Loveridge to be freed.
Loveridge was convicted of the manslaughter of 18-year-old Thomas Kelly in 2012 and is serving a 10-year jail sentence.
New South Wales police this week warned Fifita against further contact with childhood friend Loveridge due to concerns "about the potential for organised crime to infiltrate sport".
The Sharks and the NRL have affirmed their commitment to working with police in order to protect the competition from criminal elements.
Fifita meanwhile has denied reports the 'FKL' letters seen written on an armband stood for 'Free Kieran Loveridge'.
An official Cronulla statement read: "In relation to assertions that letters worn by Andrew on his armband earlier in the season in any way refer to Loveridge being freed, the player vehemently denies them."
Fifita acknowledged he has known Loveridge since childhood and added: "I fully understand and accept the seriousness of the crime committed by Loveridge, the devastating impact it has had on the Kelly family and the need for Loveridge to serve his time.
"I want to extend my sincere apologies to the Kelly family for any distress caused to them by having this tragic matter back in the media."
An NRL statement confirmed the integrity unit will conduct further inquiries into the matter, with chief executive Todd Greenberg adding: "Clearly it is inappropriate to use any club clothing or accessories to support someone with a criminal conviction.
"Players are generally free to support any person or cause they like. But in circumstances such as these, they cannot use our game as a platform to do that.
"We understand players have a life outside their club and the game and that may include mixing with people who have gone down the wrong path in life.
"But players must ensure they do not engage in any activity which damages our game."