Newcastle star Jarrod Mullen is likely to have played his final NRL game, with his B-sample also reportedly returning positive to a banned steroid.
Mullen is on a provisional suspension from the NRL after returning a positive sample to Drostanolone last November in an out-of-season test.
However, the Seven Network on Thursday evening reported Mullen's second test had also come back positive. He is facing a four-year ban by the Australian Sports Anti-Doping Authority.
Aged 29, his rugby league career is all but over.
It is understood a number of Mullen's Knights teammates had been blood-tested, while laptops and mobile phones had also been seized.
In a statement provided to the Seven Network, ASADA said it would investigate further to try to determine where Mullen sourced the steroid and whether other Knights players were involved.
"The role of the people surrounding the athlete and any other issues pertaining to the use of the substance by the athlete - in doing so, we pursue and follow any leads as part of that process," the statement read.
Mullen is the first NRL player to test positive to steroid use since former Sydney Roosters forward Martin Kennedy was hit in 2015 with a ban for two years and nine months.
Mullen has played 211 games for the Knights since making his debut in 2005 and had been considered an integral member of their line-up ahead for the 2017 season.