On March 12, an Express Mail package arrived at the U.S. Postal Service's Incoming Mail Facility in Linthicum, outside Baltimore. Its handwritten label gave a name and address for the sender, Tim Flores in Germantown, Md., and the recipient, John Velazquez of San Francisco. Drugs dealers frequently use handwritten labels, postal inspectors know, and illegal drugs frequently are mailed from San Francisco to Maryland while cash to pay for drugs is frequently mailed to San Francisco from Maryland. Suspicions that contraband might be in the package are raised further because Velazquez' address in San Francisco is for a commercial mail facility, which, postal inspectors know, are frequently used for shipments of contraband.