WASHINGTON –  A new report released Friday by the US Centers for Disease Control and Prevention points to no single product or brand that is responsible for the thousands of vaping-related lung illnesses reported across the United States.

The agency on Thursday reported 2,291 confirmed cases of lung injury in the US related to vaping as of December 4 across all 50 states, the District of Columbia, Puerto Rico and the US Virgin Islands. The CDC has also reported 48 confirmed death in 25 states and the District of Columbia.

Although investigators have linked vitamin E acetate, a thickener used in some vaping products, to many of the lung injuries, the CDC said in its latest report that “many substances and product sources are being investigated, and there might be more than one cause.”

While the CDC report also suggested the outbreak of illnesses may have peaked in September, it is still recommending that users avoid vaping any products that contain THC, “especially those acquired from informal sources like friends, family members, or in-person or online dealers.”