Former boxing champion Floyd Mayweather and music producer DJ Khaled have become entangled in an alleged multi-million dollar cryptocurrency scam.

Both Mayweather and Khaled were involved in the promotion of Centra Tech's 2017 "initial coin offering" (ICO), whereby funds are raised through the sale of cryptocurrency tokens.

Two of the founders of Centra Tech – Sam Sharma and Robert Farkas – were later arrested over charges relating to securities fraud and wire fraud and a class action lawsuit was brought against them.

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According to the ICO, Centra Tech had partnered with Visa and Mastercard in order to issue a debit card for cryptocurrencies – a claim denied by Visa.

A civil suit filed by the US Securities Exchange Commission (SEC) stated that the ICO was promoted by "touting nonexistent relationships between Centra and well-known financial institutions," thus misleading investors.

In an interview on the Neocash Radio podcast in August 2017, Sharma claimed: "Internationally we currently have our license with Mastercard to service international clients, domestically we have a Visa partnership, so we're able to issue Visa cards domestically."

Two months later, Visa issued a cease-and-desist against Centra from making any reference to Visa in its promotional materials. A spokesperson for Centra Tech was not available for comment at the time of writing.

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The SEC filing stated: "Both Sharma and Farkas were aware, were reckless in not knowing, or were negligent in not knowing that Centra had no relationship with Visa or Mastercard at the time of the Centra ICO."

Within six hours of launching its initial coin offering on 2 August, 2017, the company announced that 2,500 people had contributed 113,924 units of the ethereum cryptocurrency ether. At the time this was the equivalent of around $25 million.

Mayweather promoted the project on Twitter and Instagram, telling his 8 million followers on Twitter in September 2017: "Centra's ICO starts in a few hours. Get yours before they sell out, I got mine."

Floyd Mayweather promoted Centra's ICO alongside a picture displaying his boxing belts (Twitter/ Screenshot)

A Facebook post that has since been deleted stated: "As usual I'm going to win big with this one!"

Mayweather's involvement with other ICOs led him to call himself "Floyd 'Crypto' Mayweather" on his social media channels, a play on his nickname Floyd 'Money' Mayweather.

In a since-deleted post to his 12 million Instagram followers, DJ Khaled described the project as a "game changer."