The NRL has confirmed ASADA held a series of meetings on Wednesday with former and current players and their legal representatives.
"We are aware that ASADA has commenced the process of issuing show cause notices to certain players who were at the Cronulla Club in 2011," a spokesman said.
"This is a process that may or may not lead to players being placed on the register of findings.
"This process is governed by the National Anti-Doping Scheme and players have been invited to make submissions to ASADA in response to the notices."
The NRL will make no further comment until we have received further advice from ASADA.Read the Sharks' statement
Meanwhile the Cowboys and Knights have released statement on their websites.
The Cowboys' statement reads: "The North Queensland Cowboys understand that NRL squad member Matthew Wright has received a “show cause” from ASADA following investigations into the Cronulla club in 2011.
There has been no information provided directly to the Cowboys from ASADA at this stage.
A Cowboy since the start of this season, Matthew was not part of today’s meetings in Sydney but will see his solicitor, who is managing the process on their behalf, to receive advice and more information on the matter.
The Cowboys will not be making any further comment on any matter relating to the ASADA investigation until further notice."
The Knights' statement reads: "The Newcastle Knights has been made aware players from the Club have been issued with show cause notices from ASADA on Wednesday, relating to matters that took place at a previous Club.
"The players have been given a time frame to work through this process with their legal representatives.
"The Club is providing support for the players and won’t be making further comment until the matter is finalised."