"More information is needed to know what is causing these diseases," Ileana Arias, an official with the CDC, said Friday.
The Illinois patients have ranged in age from 17 to 38, according to the state health department.
State health departments are handling most investigations into respiratory diseases.
"We're at a relatively early stage of understanding," Mitchell Zeller, director of the FDA's Center for Tobacco Products, said Friday. The collective agencies were throwing "a lot of resources at this," he added, but part of the problem was that state investigations were not always complete, making it difficult to form a clear picture.
One theory, as yet unproved, is that illnesses may result from substances that are thought or known to be toxic in vaping products that use heat to vaporize nicotine and other inhalants.
Brian King, deputy director of translation research at the CDC's Office on Smoking and Health, said potential irritants include "ultrafine particles, some heavy metals, such as lead," and, he said, "there are also concerns about some flavors. "
But, he added, "We don't specifically link any of those ingredients to specific cases."
Dr. Michael Lynch, medical director of the University of Pittsburgh Poison Center at the University of Pittsburgh Medical Center, said the lung injury doctors there see are consistent with chemical inhalation injuries.
Dr. John Holcomb, a pulmonologist in San Antonio, Texas, noted that the FDA has no control over the ingredients used in vaping products.
"The problem is we don't know what's going on through these devices, of which there are five or six hundred different kinds," he said. "We have to assume that some of them may be dangerous and some may not be dangerous."
Others have suggested that individuals are emptying out commercial nicotine pods and filling them with a combination of THC oil and other chemicals.
If respiratory illnesses can be traced to THC-laced vapors, public health officials and doctors have expressed concern that it may be a second emergency signal in the fight against youth vaping: the growing use of unregulated, bootleg or black market cannabis liquids.
"We believe they are getting empty cartridges somewhere and filling them with their own products," said Nancy Gerking, assistant director of public health in Kings County, Calif., Who has had numerous cases. "We don't know what they're cutting it with or anything else."
Until recently, these cases have been off the radar of most doctors and public health officials who were already struggling to stop young people from vaping standard e-cigarettes. But cannabis liquids and oils have become more widely available online and in many stores. And because the ingredients may not be disclosed at all, unsuspecting consumers may be exposed to a cocktail of hazardous chemicals.
The e-cigarette market has expanded to counterfeiters and a range of devices that can be packed with various substances, including marijuana, but also various flavors and conclusions that may be mixed inexpertly.
Public health officials, however, declined to say if they were still seeing a pattern that would clarify whether the problematic products were made by mass-market companies or counterfeiters, or whether the inhalants involved were standard to many vaping products or made or mixed by them. consumers themselves.
The recent revelations could further complicate the tarnished image of the growing e-cigarette market. For several years, industry and top-selling companies, such as Juul, have faced scrutiny because of the rising popularity of e-cigarettes among teenagers, which threatens to create a new generation of nicotine addicts that may become eventual cigarette smokers.