Three players have tested positive for banned substances, the Rugby Football League's Doping Control Panel announced on Tuesday.
London Broncos winger Dominic Peters has been suspended from playing for 12 months after testing positive for stanozolol.
Stanozolol is the same steroid for which Canadian sprinter Ben Johnson was stripped of his 100m gold medal at the 1988 Seoul Olympics.
The RFL's doping panel also suspended Martin Moana for 28 days after the Halifax player tested positive for ephedrine.
A third, unnamed player was charged with providing a sample containing an unspecified banned substance.
After taking into consideration the mitigating evidence presented at the hearing, the player was given a suspended 12 month sentence and fined £2,500.
The London Broncos said they "appreciate and acknowledge the seriousness" of Peters' offence, but have not released an official statement.
The Acton-born winger is the first London-born talent to play at the top level for the Broncos.
He made an impression as a second rower and won a debut for the club five years ago, scoring nine tries over the next two seasons.
He continued to excel as a winger, but faded from the first-team frame in 2001 after scoring one try in 16 appearances last season, and has spent part of the current campaign with London Skolars.