8:02 AM PT: Law enforcement tells TMZ ... the reason cops searched the bags is because they received an anonymous tip someone in Justin's party had drugs in their luggage. Justin's bags, along with the bags of his entourage, were searched. Cops found nothing.

Justin Bieber's reputation apparently precedes him ... a drug-sniffing dog rooted through his posse's luggage at the Ft. Lauderdale International Airport.

Justin was busy posing with fans as the police pooch did his thing. As far as we can see, the dog turned up nothing and everyone made their flight ... eventually.

The Biebs was in Miami over the weekend, partying with Lil Jay Z and Lil Kevin Hart.