Wasps forward Ashley Johnson has been provisionally suspended by the Rugby Football Union (RFU) after he failed an out-of-competition drugs test in February.
South African flanker-cum-hooker Johnson, 31, is unavailable for selection "pending final determination of the matter" and his club has pledged its support as the cause of the result is investigated.
"The club is aware that a prohibited substance was reportedly found in an out-of-competition doping control sample provided by Ashley Johnson on Feb. 7 2018," a Wasps statement read.
"He has been provisionally suspended by the RFU pending final determination of the matter and is therefore currently unavailable for selection.
"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.
"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."
News of Johnson's failed test comes just three days after the RFU handed Yorkshire Carnegie forward Brandon Staples a four-year ban after he tested positive for three steroids last August.
