The Centers for Disease Control on Thursday reported that 275 new cases of vaping-related illnesses and three more deaths have been tracked across the country since last week. The mysterious illness had sickened 530 people across 38 states and killed nine as of last Thursday, but those numbers increased to 805 people sickened across 46 states and 12 deaths by this Thursday. The spike has come as no surprise to CDC officials. During a public hearing on Tuesday, Anne Schuchat, principal deputy director of the CDC, told the House of Representatives that “hundreds of more (cases)” would likely crop up by the next weekly data update.

According to the CDC, all reported cases have a history of e-cigarette product use or vaping, but the similarities stop there. “The investigation has not identified any specific e-cigarette or vaping product (devices, liquids, refill pods, and/or cartridges) or substance that is linked to all cases,” the CDC reports. The inconsistency of products, additives, or substances used in the devices—varying between THC, nicotine, and patients who “have reported using THC and nicotine”—has made it difficult to find a link.

The CDC is working with states to create a case definition “to classify confirmed and probable cases in a consistent way” in order to better understand the disease. In the meantime, the agency recommends not using any e-cigarette or vaping products, especially if purchased off the street, as substances used could have modifications not intended by the manufacturer.