The NRL has confirmed it is investigating the Cronulla Sharks over alleged illegal payments to players during the 2015 and 2017 seasons.

NRL CEO Todd Greenberg will address the media at 2pm on Wednesday at Rugby League Central to discuss inquiries into salary cap matters at the Sharks.

A spokesman for the NRL has confirmed that the Sharks had asked the Integrity Unit to make inquiries into salary cap matters at the club.

"Those inquiries are on-going so we are not in a position to comment further at this stage," a NRL spokesman said on Tuesday night.

"However, based on the information available, the Sharks and all other clubs are salary cap compliant for 2018."

The club won the Telstra Premiership in the 2016 season beating Melbourne Storm. But the irregularities that the Sharks uncovered themselves under an audit earlier this year, reportedly do not relate to the title-winning season.

The matters were raised when new CEO Barry Russell took over in March this year from former chief executive Lyall Gorman.

It's understood Gorman, who was in the role from November 2014 until the end of the 2017 season, has not been contacted in regards to the NRL's investigation to date.

"I have no context in the matter other than what was on the media last night and the club and NRL statements," Gorman, now chief executive at Manly, told NRL.com.

"Until I learn more about the details of the investigation I can't make any useful comment."

There had also been a change in chairman from Damian Keogh to Dino Mezzatesta, who took over the reins in June 2017.

Russell had auditors go through all the club's finances so he could get a full handle on the situation as he began his new role.

A report by News Corp on Tuesday claimed an irregular payment to a player had been discovered in 2015. But there were other questionable third party payments (TPAs) made in 2017 and the total amount could be around the $250,000 mark.

Under NRL rules, while there is no limit on the amount of TPAs for players to be paid on top of their salaries, clubs cannot negotiate them. They must be done at an arm's length from club officials and executives but also must be declared to the NRL.

The Sharks released a statement confirmed these "salary cap discrepancies" related to historical third-party player payments, and were discovered during a Club instigated governance review.

"The Sharks self-reported to the NRL and asked for their assistance in investigating this matter," it said.

"The club is fully cooperating with the NRL Integrity Unit, allowing them access to any information they require to complete their investigation.

"The discrepancies occurred under previous club management. This is a historical issue, we are currently salary cap compliant for the 2018 season having passed our mid-season salary cap review."

Cronulla forward Luke Lewis told NRL 360 he had been unaware of the issue until the reports surfaced.

"We haven't been to training, I've literally come in here and seen the paper and it said the Sharks are under salary cap allegations. That was it," he said.

"I'm very surprised by it. I'd love to see where it's all going and what's happening but my guess is as good as anyone else, I don't really know what's happening at the moment.

"I don't see anything happening in the next week or two. Whatever happens happens. There's nothing we can do now. The past is the past."

The Sharks sit fourth on the ladder heading into their final round clash against the Bulldogs at ANZ Stadium on Sunday.