LONDON, England (AP) — The Commonwealth Games Federation says former 400-metre world champion Amantle Montsho’s backup sample also tested positive for doping after competing in Glasgow.

The Botswana runner’s samples showed traces of the banned stimulant methylhexaneamine after she surrendered her Commonwealth title last month by coming fourth in the women’s 400-metre final in Glasgow, Scotland.

That race was swept by Jamaica with Stephenie McPherson winning gold, Novlene Williams-Mills silver and Christine Day taking the bronze.

CGF chief executive Mike Hooper says Montsho was informed about the results of her ‘B’ test result on Friday, and has until August 22 to respond to the federation.

The case will then be passed to track and field’s governing body, the IAAF, which can impose a ban. The 31-year-old Montsho won her world title in 2011.

The only other positive test in Glasgow led to 16-year-old Nigerian weightlifter Chika Amalaha being stripped of her gold medal.