The NRL is confident the integrity of its final series won't be compromised, believing the Roosters didn't use banned substances during their association with a controversial nutrition company.

The minor premiers cut ties with weight loss and nutrition company Nubodi earlier this year, claiming players were tested for human growth hormone without the consent of club officials and staff. Six players - including Boyd Cordner, Sam Moa and Roger Tuivasa-Sheck - recorded elevated readings for HGH in test results found on a phone seized from an organised crime figure. It's understood the Australian Crime Commission has investigated how the information came to be on that person's phone.

However, there are no concerns about the Roosters taking their place in the grand-final qualifier, or the grand final itself, should the Bondi Junction outfit make the decider.

''The NRL integrity unit was made aware of these matters earlier this year and we have no reason to suspect a doping issue,'' said integrity unit boss Jim Doyle. ''ASADA [the Australian Sports Anti-Doping Authority] has also known of the issue for some time and we are not aware of any investigation on their part into those matters. Over the course of this year we are identifying a range of issues that will lead to significant changes in the way we monitor and review sports-science programs across all clubs.''

The revelations couldn't come at a worse time for the Roosters as they prepare to take on Newcastle at Allianz Stadium on Saturday night. The tricolours are the favourites to take out the title but will have to deal with an unwanted distraction during their final preparations.

''As is the case with all clubs, players have been regularly and extensively tested throughout the season by ASADA and the club has fully co-operated with the organisation's routine tests,'' the Roosters said in a statement.

''In relation to matters raised in the media today, there has been full voluntary disclosure with the NRL's integrity unit over many months and the club has not been contacted by ASADA.

''We reinforce that the club maintains the absolute highest standards in its own policies and governance, and as a club we have nothing to hide.''

The NRL informed ASADA once the Roosters had drawn their integrity unit's attention to the issue.

''I'm not aware that there's a further anti-doping issue or that ASADA are investigating that any further,'' ARL Commission boss Dave Smith said on Thursday. ''The whole point of the integrity unit is not just to react to things but build stronger systems in the game. The Roosters made us aware of the issues and made ASADA aware. We don't believe there is a drug issue to follow through on.''

A former Roosters lower-grade player, Ben Darcy, is a person of interest in ASADA's investigations into rugby league. Darcy was an employee at Nubodi for about six months before he was sacked by owner Sean Carolan. Carolan, who was introduced to the Roosters through client and prop forward Martin Kennedy, has denied providing Roosters players with HGH.

Former Canberra winger Sandor Earl, who was in a paid interview that screened on the Nine Network on Thursday night, and Darcy are friends from school and their time at the Roosters. Earl is facing the prospect of a ban of up to four years for doping offences, including trafficking, during his time at Penrith in 2011.

In relation to the Roosters HGH level results recorded on a phone, an NRL spokesperson said: ''Clearly that is something that the ACC was looking at. The Roosters have been public in saying they ended their association with the company.''

The integrity unit continued to monitor and work with clubs.