>> herdman: it's cheaper to buy fentanyl. and because it's so potent, you can cut it in a way that you can deliver far more doses with a little bit of fentanyl. so it's a profit motive for them. >> pelley: where did all this stuff come from? >> herdman: it's from china. it's manufactured in china. these are all related to cases that involve the mail or the use of the postal system. so this, somebody put this into a box, sealed it up and sent it through the postal system. >> pelley: the united states postal system has been, for many years, the most reliable way to smuggle drugs from china to the u.s. >> rob portman: that has to stop. it should've stopped years ago. >> pelley: ohio senator rob portman's staff investigated the traffic. what did your office's investigation find? >> portman: shocking, what we found. which was that people who were trafficking in fentanyl told us, if you send it through the post office, we guarantee delivery. if you send it through a private carrier, not so. >> pelley: that's because after 9/11, all