Not true:
"SPOKANE, Wash. - SWAT raided a Spokane home on heroin warrant. It happened just before 11 am Friday morning at a duplex home on the corner of 4th and Altamont. Details were not immediately known but authorities on scene say they were serving a warrant related to heroin."
http://www.khq.com/story/21437261/swat-situation
How do police obtaining a warrant? In part by establishing probable cause. How is probable cause determined in the US:
"Probable cause can be based on either direct observation by the police officer, or on hearsay information provided by others."