Thirteen of the twenty best-selling drugs in the U.S. are made in plants in Puerto Rico. But an investigation found dozens of examples over four years of lapses in quality control in the Puerto Rican pharmaceutical industry.

Even modern Puerto Rico drug plants, under the watch of U.S. regulators, have failed to keep laboratories sterile and have exported tainted pills.

FDA inspections from 2003 to 2007 found many problems, including machinery pins ending up inside bottles of Effexor (a depression treatment) and Protonix (a heartburn drug), and Metformin pills (a diabetes treatment) being sent to the U.S. even though they were known to contain small amounts of metal particles.