According to TMZ, who spoke to a representative for the Stockholm, PD, around 7:10 pm on Wednesday night, April 24th, an officer detected the smell of weed coming from Justin Bieber's tour bus.  The bus was parked right outside of the Grand Hotel at the time when the officer noticed the potent scent.  Apparently, after Justin's tour bus pulled off towards the Globe Arena, the officer then contacted a narcotics unit that was able to obtain a warrant in order to search Bieber's ride.  

The bus was parked in the garage of the Globe Arena with no one inside at the time that the authorities searched the vehicle.  Although it hasn't been officially specified which drug(s) were found on the tour bus, local newspapers claim that the contraband in question was in fact marijuana, along with a taser.  

Due to the fact that the bus was empty, no charges will be placed on Bieber or any of the passengers because police have no clue as to who was responsible for initially bringing the drug onto the bus.  However, hours before the minor drug bust, Bieber was seen with his buddy Lil Za -- the same person Bieber was spotted smoking weed with inside of an L.A. home earlier this year.

Source: tmz.com