Former world and Commonwealth champion Amantle Montsho has been provisionally suspended after failing a doping test following the women's 400m final at Glasgow 2014.
The A sample of Botswana's Montsho, who finished fourth in the 29 July final, tested positive for banned stimulant methylhexaneamine.
A further test of the B sample will take place on Monday in London.
Montsho, 31, won Commonwealth gold at Delhi 2010 and the world title in 2011.
Her gold medals at Delhi and Daegu were her country's first at a Commonwealth Games and World Championships respectively, and she also won silver at the 2013 World Championships in Moscow, losing out to Great Britain's Christine Ohuruogu in a dramatic photo-finish.
She missed out on a medal at Glasgow as she tied up badly in the final 100m and finished behind the Jamaican trio of Stephanie McPherson, Novlene Williams-Mills and Christine Day.
Montsho told the BBC earlier this year that she would quit athletics after the Rio 2016 Olympics and was aiming to become a basketball player.
|Amantle Montsho's major achievements|
|World Championships||Gold (Daegu 2011)Silver (Moscow 2013)|
|Commonwealth Games||Gold (Delhi 2010)|
A statement from the Commonwealth Games Federation read: "The athlete's A sample was found to contain methylhexaneamine, prohibited as a stimulant under class s6 of Wada's Prohibited List.
"Upon receipt of the analysis of the athlete's B sample, the court will reconvene to consider the matter further."
Montsho is the second athlete to have failed a drugs test at the Games.
On Friday, 16-year-old Nigerian weightlifter Chika Amalaha was stripped of her gold medal after her A and B samples tested positive for banned substances.
The samples contained amiloride and hydrochlorothiazide, which are both prohibited as diuretics and masking agents.