Usain Bolt will have to hand back one of his nine Olympic gold medals after Jamaican team-mate Nesta Carter tested positive for a banned substance.

Carter was part of the Jamaican quartet that won the 4x100m in Beijing in 2008.

His was one of 454 selected doping samples retested by the International Olympic Committee (IOC) last year, and has been found to contain the banned stimulant methylhexaneamine.

Bolt, 30, completed an unprecedented 'triple triple' in Rio last summer.

He won gold in the 100m, 200m and 4x100m relay to add to his successes in the same events in 2008 and 2012.

Carter, 31, was also part of the squad that won the relay in London five years ago.