Officials in the US have identified a substance that's a potential 'culprit' behind the mysterious lung disease outbreak that has been linked to vaping.
Recent months have seen more than 2,000 cases of 'confirmed and probable' lung injury cases across the US, associated with the use of e-cigarettes.
Officials have also confirmed 39 deaths across two dozen states.
In an update yesterday, the Centre for Disease Control (CDC) said all the samples tested from 29 patients across multiple states showed the presence of Vitamin E Acetate - making it a "very strong culprit" for the lung injuries.
Dr Anne Schuchat, principal deputy director of CDC, said the findings are significant as authorities have now detected a "potential toxin of concern" for the first time.
She observed: "Vitamin E Acetate is a vitamin found in many foods and is also available in supplements and cosmetic products like skin cream.
"[It] is also a known additive used to dilute liquid in e-cigarette or vaping products that contain THC."
She added: "Vitamin E Acetate does usually not cause harm when swallowed as a vitamin supplement or applied topically to the skin.
"However, previous non-CDC research suggests that when Vitamin E Acetate is inhaled, it may interfere with normal lung function."
Dr Schuchat stressed that further studies are need to establish a definitive link between the substance and the disease, noting that there may also be more than one cause of the outbreak.
She repeated the CDC advice to not use e-cigarette or vaping products that contain THC, "particularly from informal sources like friends or family, online dealers or the illicit market".
However, she also stressed there were a "small proportion" of cases where the patients have reported only using nicotine-based vaping products - and recommended people consider refraining from all e-cigarette use while their investigation continues.