COLLINGWOOD has confirmed defender Sam Murray is being investigated by the Australian Sports Anti-Doping Authority (ASADA).

As reported first by Damian Barrett, Murray recently recorded an elevated reading in a post-match drugs test, possibly the Magpies game against Richmond at the MCG on July 28.

It's believed Murray was made aware of the abnormalities in his sample late last week.

Collingwood said ASADA was leading the investigation and was in charge of the timing.

The Magpies also confirmed Murray had sought independent legal advice.

In a statement on Friday morning, Collingwood chief executive Mark Anderson said the club had a strong stance against drugs in sport, but was also aware of supporting the 20-year-old's welfare.

"I would like to reinforce that Collingwood is unequivocally committed to the cause of eliminating drugs in sport," Collingwood chief executive Mark Anderson said.

"We fully support all anti-doping policies and our athletes understand the rules in place. Collingwood has worked hard to develop a culture of professionalism and respect within its teams and we are making great progress.

"It would be inappropriate to pre-empt the outcome of the ASADA process.

"In addition to ensuring we comply fully with the ASADA process, we are also ensuring that we support Sam as a person.

"We are not able to make any further comment until all of the facts are gathered, the investigation completed and a determination reached."

On Thursday of last week, Murray was selected in the Magpies team to play against Port Adelaide at the MCG on Saturday, but on Friday night he withdrew from the team, with the club citing "personal reasons" for his unavailability.

The substance detected by ASADA was an illicit drug, which when detected on match-day is regarded as performance enhancing and thus carries the potential of a four-year ban from football.

The maximum sanction can be mitigated under certain circumstances.

As per protocols, if an ASADA test for drugs records a positive result, it is viewed as the A-sample. The athlete is informed of the finding, and it is at his or her discretion whether a B-sample is required.

The Murray situation is at this juncture, and it may take months for it to reach a final outcome.

Murray didn't train with Collingwood on Thursday and has been absent from the club all week.

Depending on how he and his managers choose to deal with his situation, Murray has the option of taking an immediate provisional suspension, which would be taken into account when and if an official suspension is handed down.

Murray was a Sydney Swans listed player after being taken as a NSW priority zone selection in 2016. He failed to play a senior game with the Swans and was traded to Collingwood last year in exchange for the Pies' second-round selection in this year's national draft.

He started the year in solid form, playing the first nine matches, before being dropped to the Collingwood VFL team. He returned to the seniors for rounds 18, 19, 20 and 21 before withdrawing from last week's game.

The Richmond game was round 19.

The AFL refused to comment when asked about Murray on Thursday night.

Collingwood players Josh Thomas and Lachie Keeffe in 2015 were banned for two years after being detected for taking banned substance Clenbuterol.

On that occasion, the Clenbuterol had been contained in a batch of illicit drugs taken by Thomas and Keeffe, along with several other AFL-listed players, during a music festival in St Kilda.

Thomas has been a very good player in Collingwood’s rise up the ladder this season, playing every match and booting 34 goals.

ASADA has declined to comment on the matter.

"Under our legislation and the World Anti-Doping Code, ASADA is unable to confirm or deny the existence or otherwise of any possible anti-doping investigation," an ASADA spokesperson told AFL.com.au.