photo courtesy of Terry RichardsonLuckily for the pot-smoking princess, she wasn't on board at the time!

Ten of the 24-year-old R&B starlet's tour buses were stopped on the Ambassador Bridge, which separates Windsor, Canada and Detroit, Michigan, and TMZ reports that law enforcement officers searched all of the vehicles after smelling marijuana on one of the buses.

Authorities brought drug sniffing dogs on board, at which point they found "a small amount" of marijuana on one person on the bus, who was cited with a civil penalty.

No word on where RiRi was (and she has yet to tweet about the incident), but she's definitely loud and proud when it comes to her use of the drug. When asked about why she posts so many photos of herself smoking on the internet, she recently told Elle UK, “I’m posting pictures of myself smoking pot to tell the truth about myself. I’ve got so much to think about, why bring all this extra s**t by being dishonest?"