Rihanna Tour Buses Stopped At Border: Weed Found.

Rihanna's tour buses were stopped at the border between Michigan and Canada, and law enforcement sources tell TMZ ... authorities found weed.
A total of 10 buses were stopped at the Ambassador Bridge, which separates Windsor, Canada and Detroit.  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.  We're told he was cited with a civil penalty.

Rihanna was not on any of the buses.