"It's a tragedy for Jarrod, it's a tragedy for his family, it's a tragedy for the club," Mr Gardner told media in Mayfield on Tuesday. 

"This tragedy probably has a few more acts to play out before it's finished."

Mr Gardner confirmed several elements of reports including that Mullen had overdosed, but said he believed other parts were incorrect.

"To the best of my knowledge none of our top 36 were at any of those parties, I think the reports aren't accurate, I don't know why they've been reported but it certainly doesn't represent the facts," he said.  

"They've also got the issue with Jarrod wrong. Jarrod did overdose, he did not overdose at the party. He was found at home by his family.

I can only say to you again, what a tragedy for the family. Anybody that's a parent who finds themselves in this situation would understand how difficult this is for everybody. 

"This keeps getting played out again and again and again and it's just wrong."

While he pledged that Newcastle would "do everything we can to assist Jarrod and his family", Gardner noted the doping ban in place since 2017 remained a factor.

"We must understand that he's been barred of contact with the game for the next four years," he said. 

"I can assure you in rugby league we do the absolute best we can to rehabilitate and look after people.

"We're going to do our best. We're also going to use it as an example of what not to do for our players so they understand. 

"Jarrod's journey from the absolute pinnacle of our game to where he is today brings a tear to my eye. 

"This young man was a Wests junior, I've known him since he was a child, I've known his family for many years, he's a distant cousin.

"We don't want to see this happen to anybody ever again."  

Former Newcastle Knights halfback Jarrod Mullen is being investigated by police in relation to an alleged drug supply syndicate in Newcastle and Lake Macquarie.

Mullen, who played 211 games for the Knights since debuting in 2005, and also represented NSW in the 2007 Origin team, is reportedly now linked to an illicit drug supply investigation, headed by Strike Force Castlestead.

The strike force was formed in September 2018 ''to investigate and dismantle an alleged drug supply syndicate operating across the Newcastle City and Lake Macquarie Police Districts,'' a statement from NSW Police said on Monday.

Since December, five search warrants have been executed and 10 people have been arrested and charged in relation to a range of matters including supplying a large commercial quantity of a prohibited drug and knowingly participating in a criminal group. Investigations by the strike force continue and further arrests are anticipated, NSW Police said.

Mullen, who is understood to have left Newcastle, is serving a four-year ban after testing positive for steroids in 2017.

He was banned until 2021 after he was found guilty of taking the steroid Drostanolone by the NRL's anti-doping authority.

Mullen delivered a positive result for Drostanolone after a routine swab test during pre-season training in 2016.

In March 2017, the Australia Sports Anti-Doping Authority (ASADA) recommended Mullen be banned for four years however he chose not to accept the punishment and appealed to the NRL anti-doping tribunal.

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He pleaded for leniency, arguing he was not attempting to gain a competitive advantage but was hoping to repair his body after suffering a second serious hamstring injury in a year.

But he was suspended after the anti-doping tribunal, chaired by former High Court judge Ian Callinan, found in May 2017 that he had violated the game's anti-doping policy.

"As we have said all along, this has been a disappointing matter for all parties,'' Matt Gidley, the then Knights chief executive, said at the time.

''We wish to reiterate this matter took place independently of the club."

He acknowledged Mullen's talent.

''It is important to acknowledge Jarrod made a significant contribution to the club over a long period of time and that adds to the disappointment in how he now departs the club," he said.