The Centers for Disease Control and Prevention reported on Thursday that 34 deaths related to vaping have been confirmed—more than double the 12 deaths reported by the agency around the same time last month. According to the CDC, as of Oct. 22, there have been 1,604 cases of “e-cigarette, or vaping, product use associated lung injury” reported across 49 states, and 34 deaths across 24 states. Last month, only 805 people sickened across 46 states had been reported. The jump could be related to a better understanding of the mysterious disease amongst doctors, leading to an increase in identified cases. Identifying the symptoms, however, has not yielded an answer as to why they are occurring. “This complex investigation spans almost all states, involves over a thousand patients, and a wide variety of brands and substances and e-cigarette, or vaping, products,” the CDC reported on Thursday. “Case counts continue to increase and new cases are being reported, which makes it more difficult to determine the cause or causes of this outbreak.”