MINNEAPOLIS (AP) – Investigators are focusing on marijuana-derived THC in the Minnesota cases of teens and young adults who developed vaping-related lung illnesses this summer. The Star Tribune reported Tuesday that health officials have interviewed eight of 15 patients in Minnesota who have been hospitalized for severe respiratory illnesses with confirmed links to vaping.   Rich Danila of the Minnesota Department of Health says all eight inhaled THC, the compound in marijuana that gives it its high.