Amantle Montsho has been provisionally suspended

Former world 400m champion Amantle Montsho has failed a drugs test at the Commonwealth Games.

The 31-year-old from Botswana tested positive for the banned stimulant methylhexaneamine after finishing fourth when defending her Commonwealth title in the 400m final in Glasgow last Tuesday.

Montsho is the most high profile athlete to have failed a drugs test at the Games, having won the world title in 2011 before finishing second behind Christine Ohuruogu last year.

She has been provisionally suspended and will have her B sample tested on Monday.

A statement on Saturday from the Commonwealth Games Federation read: “In accordance with the CGF anti-doping standard for the XX Commonwealth Games, the CGF federation court conducted a provisional hearing this afternoon to consider an adverse analytical finding submitted by Amantle Montsho of Botswana, after the women's 400m final on July 29.

"The athlete's A sample was found to contain methylhexaneamine, prohibited as a stimulant under class s6 of WADA's Prohibited List.

"Ms Montsho was notified of her A sample result and has asked for her B sample to be tested, which will take place at the accredited laboratory in London on Monday August 4.

"Ms Montsho attended the provisional hearing of the federation court, presided by CGF vice-president Bruce Robertson, which ruled that the provisional suspension of the athlete will continue.

"Upon receipt of the analysis of the athlete's B sample, the court will reconvene to consider the matter further."

Montsho finished fourth at the London 2012 Olympics and she was favourite for the world title in Moscow last summer, only to lose out to Ohuruogu by just four thousandths of a second.

She was expected to get on the podium in Glasgow, but finished behind the Jamaican trio of Stephenie McPherson, Novlene Williams-Mills and Christine Day.

Methylhexaneamine was only added to the World Anti-Doping Agency banned list in 2010.

It is the same substance that Jamaican sprinter Yohan Blake tested positive for in 2009 and he received a three-month suspension, even though it was not then on the banned list.