London - Former South African international Ashley Johnson has been suspended by the Rugby Football Union (RFU) after failing a drugs test, his English Premiership club Wasps announced on Friday.
The 31-year-old - capped three times by the Springboks - failed an out of competition test taken on February 7 and last played for Wasps on March 4.
"Ashley is currently investigating the possible source of the substance and both he and the club are co-operating fully with the RFU in this respect," the club said in a statement.
"We are fully supportive of him in this process but are unable to comment any further at this stage due to the confidentiality of legal proceedings."
Johnson - who can play either as hooker or in the back row - joined Wasps in 2012 from South African outfit Cheetahs and signed a contract extension with the club, for whom he has turned out over 100 times, last November.