the better counterfeiters might put in 10, 20, even 30% of the active pharmaceutical ingredient that's supposed to be in the medicine. >> reporter:. >> the pfizer lab in connecticut tests thousands of pfizer products and packaging a year. it's found fake cancer medicine, fake vaccine, fake heart and cholesterol drugs, even fake chapstick. >> they'll start with the packaging, do a number of tests to see authentic versus the counterfeit or versus the questionable one, and if the packaging doesn't demonstrate that it's counterfeit, then they actually go to the medicine itself. >> this is an audio clip that pfizer gathered as part of an undercover investigation. >> we can still make 50,000 pills a month. >> wow. >> and that's by hand. >> the company shares the information with law enforcement, which then conducts the actual raids and makes arrests. those counterfeiters were caught, but plenty are not.