Police are investigating the circumstances surrounding South Sydney duo Dylan Walker and Aaron Gray being rushed to hospital for a drug overdose early on Tuesday.

NSW Ambulance confirmed both players were found in a critical condition at Gray’s apartment in Roseberry, but have since been stabilised.

It has been reported that Walker had an adverse reaction to painkilling drugs Oxycodone and Tramadol after undergoing post-season surgery last week while it was unclear how Gray came to be unwell.

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Rabbitohs CEO John Lee said the players had taken too much of the medication, but refused to use the word “overdose”.

“This is not medication that you take for fun,” Lee said.

Lee said a third party at the house had noticed the pair suffering some side effects, including vomiting and had been “fairly heavily sedated for some time”.

Lee said both Gray and Walker has shown signs of being more alert and were expected to show further improvement throughout the day.

NRL chief executive Dave Smith said the integrity unit would launch its own inquiry into the incident, but that the players’ welfare was of their utmost concern.

“Souths called the integrity unit this morning,” Smith said.

“(Integrity Unit chief) Nick Weeks is aware what’s going on, and of course, the number one priority is the welfare of these two young men.

“Any questions that need to be asked will be asked should they need to be.”

Smith was careful not to link Tuesday’s incident to illicit drugs, but re-emphasised the NRL had a strong drugs testing policy.

“There’s a very heavy expectation on our players, and we’ve demonstrated when things go wrong from time to time, there’s serious consequences that can affect your playing career,” he said.

“First it’s about confidential support, second time there are more significant consequences.

“I’m very confident with our policy, both for performance-enhancing and any other form of recreational or prescription drugs.”

The Rabbitohs, who were eliminated by Cronulla in the first week of the finals, said they were monitoring the situation.

“The club is keeping abreast of the situation and will not be making any further comment at this stage,” they said in a statement.

Walker, 20, played four games for Australia after playing a starring role in the club’s breakthrough premiership win last year.

Gray, 21, made his first grade debut this season and scored seven tries in 12 matches, earning himself a two-year extension at Redfern.