Wigan and England forward Gareth Hock is facing an automatic two-year ban after his B sample tested positive for cocaine.
Wigan Warriors confirmed on Tuesday that a urine sample was found to contain traces of Benzoylecgonine, a metabolite of cocaine, and the 25-year-old will now appear before a national anti-doping panel.
Hock's follow-up sample also tested positive and the powerful second rower now faces the prospect of a two-year suspension in line with World Anti-Doping Agency regulations.
The disgraced international forward was tested following Wigan's home Super League match against Salford on June 5 and was immediately suspended by the Rugby Football League.
In a statement, Wigan said: "The club reiterates its position of deploring and condemning the use of drugs in sport including the use of so-called recreational drugs."
Wigan would not comment further at this stage and the RFL had no comment. Hock, who is contracted to the Warriors to the end of the 2011 season, is potentially the most high-profile drugs offender in rugby league.