Fairfax Media understands between 5 and 6 per cent of NRL players received a strike after in-house testing last season revealed close to two dozen players had recorded positive drug test results.

The numbers were significantly higher than the previous season, forcing NRL officials to warn clubs of the concern around the use of recreational drugs during the off-season.

NRL integrity unit boss Nick Weeks addressed the clubs over the concern regarding the use of drugs by the  players at last week's chief executives meeting, noting a significant spike in numbers and warned clubs they would enforce stringent testing at the completion of each team's campaign.

Most of the eight clubs not involved in this year's finals have already been tested, with the Sydney Roosters (Monday), Wests Tigers (Thursday) and Parramatta Eels (Friday) having already been visited by testers after their seasons came to an end last week.

Random ASADA testing throughout the season focuses on performance-enhancing drugs on the banned list rather than recreational or "party" drugs, however the code-enforced testing focuses on a wider range of substances.

The NRL integrity unit has implemented several measures to try to stamp out the use of party drugs and the improper use of prescription drugs among its players, hiring Laverty Pathology to conduct testing.

The clubs used to have the responsibility of organising in-house testing, however the NRL has taken ownership of the task to ensure complete transparency of results.

If a player records a positive reading, the NRL notifies the doctor and chief executive of the club but it remains confidential.

If a player records a second strike, as South Sydney's Kirisome Auva'a did earlier in the season for an anomaly in his test results, they face a 12-week ban.

A third strike will see the player banned from the sport indefinitely, with an NRL spokesman saying strikes remained private between player, the NRL and his club until a third strike.

The NRL has had to endure its fair share of drug-related incidents during the past 12 months.

At the end of last season, there were grave concerns for the health of Dylan Walker and Aaron Gray when they were hospitalised after overdosing on prescription drugs in the off-season.

The incident was a huge wake-up call for the sport given the misuse of prescription drugs were considered to be prevalent among professional athletes in the code.

Sacked after second drugs breach: Former Souths centre Kirisome Auva'a. Photo: Getty Images

In May, Cronulla stood down under-20s player Jayden Walker for three months as part of the second strike policy following the disclosure of recreational substance use.

There was also the saga involving Parramatta's Corey Norman, who was caught in possession of MDMA capsules at the Star casino on the same night he dined with criminals and bikies.

Norman, as well as Junior Paulo and James Segeyaro, were later handed warnings by the police for consorting with criminals and was hit with an eight-week suspension by the Eels after he pleaded guilty to the drug possession charges in July.

The Eels five-eighth was also believed to have filmed a man snorting a white substance in a video that was attempted to be sold  to the media.

While it was never broadcasted, it threw Norman into a negative light for the second time this season.