wuhan. a hub of chemical manufacturing in china, and the city that lucy's website and others list as their placecity of 19 million, people we spoke to on the street said they had never even heard of fentanyl. >> never heard of it. people in china mail this to the united states? >> china mailed it to the usa? >> yeah, and it's very dangerous. people could die. >> of course that's very bad. >> reporter: we next pay a visit to the addresses in wuhan listed on the websites of those fentanyl-selling labs. looking for 1503. let's ask him. come on in. but here at this wuhan office park, we find a wedding planning company instead of a fentanyl manufacturer. >> they moved in last october, so the company's gone since maybe march. >> reporter: it was the same at this building, listed as the address for a company willing to sell us fentanyl online. >> human pool. that's not it. nobody in this building had ever heard of this company. so the address on their website, clearly it's a lie. >> reporter: what we found comes as no surprise to u.s. authorities, who say most of these labs are actually clandestine, un