Mall owners often talk about the importance of ancillary income — finding ways to generate extra revenue at existing properties. But this probably isn't exactly what they have in mind. Drug Enforcement Agency agents found more than 200 marijuana plants inside a 400-square-foot storage area at the Mall of the Americas in west Miami-Dade last month. They have no idea who was cultivating plants or set up the hydroponics lab. The lab did present a danger to the mall because flimsy wiring created a fire hazard. Overall, the plants could generate millions of dollars a year based on the $3,500-a-pound street value of marijuana in Miami.