Manchester City have suspended defender Kolo Toure after he failed a drug test.
Toure tested positive for a "specified substance" in a routine examination and left City with no option but to take action. The 29-year-old will take no part in first-team and reserve matches until the investigation is complete and could miss rest of the season.
The former Arsenal defender, who is the first footballer at a Premier League club to fail a drugs test since Chelsea's Adrian Mutu in 2004, faces a range of punishments from a warning to a two-year ban.
A club statement 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 a 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."
A "specified substance" is, as the World Anti-Doping Agency defines it, one that is "more susceptible to a credible, non-doping explanation".
Arsenal manager Arsene Wenger spoke to his former captain and revealed that Toure failed the drugs test after taking a diet pill belonging to his wife.
"He wants to control his weight a little bit because that's where he has some problems and he took the product of his wife," Wenger said at his Friday press conference.
Earlier this week it was revealed by UK Anti-Doping that Hamilton midfielder Simon Mensing had served a month-long suspension after failing a drugs test in seemingly similar circumstances.
The 28-year-old tested positive for the stimulant methylhexaneamine, which was present in a dietary supplement.
Toure is understood to have been left out of the City squad for the 3-0 victory over Aston Villa in the FA Cup on Wednesday because the club had been made aware of the issue.
An FA statement on Thursday night read: "The FA can confirm that a player has been provisionally suspended from playing pending investigation, having tested positive for the use of a prohibited substance."