Reports are emerging that Floyd Mayweather took an illegal injection before his much-publicised fight with Manny Pacquio in May.

It is alleged that the undefeated American was given an intravenous solution of saline and vitamins on the eve of the fight. The injection is banned by the World Anti-Doping Agency, although the substances themselves are not banned.

But intravenous injections are banned because they can be used to mask banned substances.

The US Anti-Doping Agency gave Mayweather an exemption three weeks after the fight.

However, the executive director of Nevada State Athletic Commission, where the fight took place, says USADA are not authorised to grant exemptions.

Mayweather will fight for the 49th and last time against the unheralded Andre Berto.