In line with Football Association regulations, the Manchester City defender has been suspended following confirmation that a "specified substance" was found in an A sample, believed to have been given after last month's Manchester derby at Old Trafford.
Toure has the right to request his B sample - given at the same time - also be tested. The Ivorian would then get the opportunity to go before a personal hearing.
Although "specified substances" do tend to be down the scale of drugs offences because the World Anti-Doping Agency accepts there are instances where credible explanations can be offered, they are still subject to a maximum two-year suspension.
Hamilton's Simon Mensing served a four-week ban earlier this season after testing positive for the stimulant Methylhexaneamine (MHA), which was present in a dietary supplement. However, former Sheffield United goalkeeper Paddy Kenny served a nine-month suspension after testing positive for the stimulant ephedrine.
In Kenny's case, it took two months for the case to be heard and the player's defence of the drug being present in cough medicine taken to combat an infection was countered by the notion that a professional sportsman "has a strict responsibility to ensure prohibited substances do not enter his or her body" - the words of Christopher Quinlan, chairman of the Regulatory Commission that heard the Kenny case.
Should Toure's case follow a similar timescale, that would rule the 29-year-old out until the beginning of May, even before any ban. City will presumably try to push for a hearing before that, although given the legal complexities, it might not be easy.
"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," said the Football Association in a statement on Thursday night.
It is believed City knew of the failed test on Wednesday, explaining Toure's absence from the squad for that night's FA Cup fifth-round victory over Aston Villa. The only consolation for City boss Roberto Mancini is that Vincent Kompany is expected to be available for tomorrow's Premier League encounter with Wigan at Eastlands.
The City statement which confirmed the news read: "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."