In addition to its location is the fact that Puerto Rico is a U.S. commonwealth, so passengers from there don't have to go through customs upon arriving on the mainland, said Laila Rico, a spokeswoman for the Drug Enforcement Administration.

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And literally, when you go through customs at the airport and start walking to catch a cab, you start to feel it in your throat.

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But when Zapeta tried to go through airport security, an officer spotted the money in the bag and called U.S. customs officials.

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Approved travelers get to use a kiosk to enter the country rather than waiting in often-long lines to get their passports stamped and go through Customs inspection.

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