The Bajan singer, who recently completed a promotional tour for new film Battleship, has shared numerous images from the event with fans online.
In one picture - posted on Instagram last night - Rihanna showed herself sitting on the shoulders of a bodyguard. However, a close-up image appeared to show a white powder on his head.
Fans reacted to the photograph, with more than 1,000 comments debating what it showed. While some were amused that Rihanna appeared to be "rolling up on his head", others questioned if the substance shown was cocaine.
One fan branded it the "coolest thing i have ever seen", while another commented: "Wait I'm still picking up my jaw that I dropped (sic)."
Writing on her Twitter page, the 24-year-old said: "I'm crazy, and I don't pretend to be anything else."
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Take a look through a gallery of Rihanna's holiday snaps below: