Murray is understood to have recorded the positive reading to an illicit substance which under the World Anti-Doping Agency code means it is treated as a doping offence.

Murray, 20, is believed to be under a provisional suspension as the Australian Sports Anti-Doping Authority awaits confirmation of the B sample in what is a lengthy process.

The positive test was recorded some weeks ago, and the Magpies have known about it for some time. Murray was withdrawn from the Magpies' team to face Port Adelaide last week for "personal reasons".

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Under the WADA code, Murray will be facing a ban of between two and four years, although he may be able to argue that he ingested the substance earlier than match day, which could reduce the penalty.

The substance in question is understood to be an illicit drug, which is classified as performance enhancing on match day only.

Had he recorded a positive test during the week, he would merely have a strike recorded against him under the AFL's illicit drugs code.

Murray's situation follows Collingwood's suspension of Josh Thomas and Lachie Keeffe in 2015 for two years, for taking an illicit drug which was found to be laced with the banned agent clenbuterol.

The AFL did not comment when contacted on Thursday night.

Murray had made an instant impact since crossing from Sydney to Collingwood in the off-season.

Murray’s AFL debut came in round one against Hawthorn after two seasons on Sydney’s rookie list.

Under Raiders coach Daryn Cresswell, Murray enjoyed a stellar season in 2015, polling third in the Morris Medal behind Albury’s Joel Mackie and Dean Polo, and ineligible North Albury star Nick Holman.

More to come