Health officials have located a common chemical they believe could be linked to the mysterious respiratory illness proliferating in users of vaping products across the country, The Washington Post reports. There have been 354 possible cases and at least two deaths of patients who vape reporting similar symptoms. The potential link is an oil-like substance derived from vitamin E that is used in cannabis products, according to investigators at the U.S. Food and Drug Administration. The naturally derived oil is known as vitamin E acetate, and is readily available as a nutritional and topical supplement. Due to its oil-like properties, however, vitamin E acetate could become dangerous when inhaled, investigators said. “This was the only thing that seemed to show up in 10 of the 18 cannabis products,” one New York state official said.

Despite vitamin E acetates recurring presence, officials say they are not close to closing the case and are moving forward with their broad search for the illness’s cause that includes “cutting agents” used to dilute liquids, pesticides, opioids, poisons, and toxins. “(The FDA) is looking into potential leads regarding any particular constituent or compound that may be at issue,” an agency spokesman said.