emergency in venice tonight as the historic italian city deals with the worst flooding in more than 50 years. much of venice was submerged because of an exceptionally high tide, one man seen swimming in historic st. mark's square at least one person has died the mayor is blaming it on climate change. the nbc news investigation what is making so many people sick from vaping the cdc singled out a synthetic form of vitamin e in some patients' lungs while it hasn't tested the actual thc vapor, a lab in california has. cynthia mcfadden has the first ever results showing an alarming mix of toxins. >> reporter: tonight at the labs in los angeles, considered one of the top marijuana testing facilities in the world, executives aaron riley and antonio frasier explain they have come up with a brand-new test. >> we wanted to design a system that would be able to provide reproducible results.