Manchester City's Ivory Coast international defender Kolo Toure has been suspended after failing a drugs test, his club announced on Thursday.
A statement on City's official website read: "Manchester City confirm that the FA has informed Kolo Toure that an 'A-sample' provided by him has tested positive for a specified substance.
"As result of this, he has been suspended from participating in all first team and non-first team matches pending the outcome of the legal process.
"There will be no further comment from the football club at this stage."
It is understood that Toure was not included in City's squad for Wednesday's FA Cup win against Aston Villa because the club were aware of the situation.
The failed test automatically triggered the suspension, with City left with no option but to exclude him from their plans until the conclusion of proceedings.
Toure, who turns 30 later this month, signed for City from Arsenal for £14mn (16.3mn euros) in 2009.
He was City's captain before Carlos Tevez and has 85 international caps to his name.
The most recent doping case in football involved Hamilton midfielder Simon Mensing.
The 28-year-old tested positive for the banned stimulant methylhexaneamine at the end of January and missed five matches.
Mensing maintained he was unaware he had ingested the substance while using a dietary supplement - an explanation which was accepted by UK Anti-Doping.