According to the Centers for Disease Control and Prevention, the number of vaping-related illnesses in the US has now reached about 1,300 cases and at least 26 deaths.
Anne Schuchat, a senior official with the Centers for Disease Control and Prevention (CDC), told reporters: "We're aware of a handful of individuals who have been readmitted for clinical care after discharge for lung injury".
Tetrahydrocannabinol (THC) is the main psychoactive component of cannabis and more than three-quarters of patients reported using it either exclusively or with nicotine products.
The Indiana State Department of Health reported two more Hoosiers have died from severe lung injuries caused by e-cigarette use.
Doctors studying lung tissue samples from people with vaping-related injuries have found that none of the cases had evidence of lipoid pneumonia, a rare diagnosis typically linked with people accidentally inhaling oils into their lungs.
These cases stretch across 49 states, as well as the District of Columbia and the U.S. Virgin Islands.
About 70% of the 1,043 patients, on whom data is available, are male, with 15% below 18 years of age, according to the CDC.
Most of the cases of the serious lung injury have happened in people between the ages of 16 and 29, majority having reported vaping THC.
Another 58% said they used nicotine-containing products with or without THC. The report's authors named the illness "e-cigarette, or vaping, product use associated lung injury", or EVALI. The agency says the state has also identified 95 confirmed or probable cases of lung illnesses linked to vaping.
The CDC, US Food and Drug Administration, state and local health departments, and other clinical and public health partners are continuing to investigate the multistage outbreak.
13 per cent reported exclusive use of nicotine-containing products. "I urge anyone who is using these products to consider stopping, especially if you are vaping THC".