those who got seriously ill were vaping thc, marijuana s active ingredient our cynthia mcfadden investigated what s in those cartridges. reporter: in search of answers, we went to california where you can buy thc cartridges legally and in the black market one of the leading cannabis testing facilities in the nation agreed to test both kinds looking for contamination. including vitamin e acetate commonly used in skin care, which some researchers suspect may be causing the lung injuries. i brought three different brands of thc cartridges from legal dispensaries and obtained 15 on the black market antonio fraser says they found no contaminants for the legal cartridges and illegal ones, did you find vitamin e? yes, in 13 out of 15 samples. reporter: 13 out of 15 yes. reporter: these are random random. reporter: one of the samples labeled as exotic cart mars og