US health officials on Thursday reported 33 deaths and 1,479 confirmed and probable cases so far from a mysterious respiratory illness tied to vaping
Last week, the Centers for Disease Control and Prevention (CDC) reported 1,299 cases and 26 deaths from the illness.
Investigators have not linked the cases to any specific product or compound, but have suggested vaping oils containing THC, the psychoactive ingredient in marijuana, as being especially risky.
The agency last week said there may be multiple causes behind the outbreak and that the source of the illness may not be the same across the country.
The spate of serious respiratory illnesses has led to US officials urging people to stop vaping, especially those products containing THC.