A total of 10 buses were stopped at the Ambassador Bridge, which separates Windsor, Canada and Detroit. Rihanna was not on any of the buses, reported TMZ Online.
Inspectors smelled marijuana on one of the buses and initiated a secondary bus-to-bus search.
Inspectors then brought drug-sniffing dogs on board, and one of them made a beeline for a passenger and authorities found he was in possession of pot. He was cited with a civil penalty.