The epidemic of severe lung illness related to e-cigarettes continues to grow, federal officials say, as they try to pinpoint the exact cause.

The Centers for Disease Control and Prevention said as of Thursday there were 805 cases of confirmed or suspected vaping-related lung illnesses in 46 states and the Virgin Islands — up more than 200 since last week. Twelve deaths are reported.

Many of the victims say they used vaping products containing THC, the compound in marijuana that causes the high. But others say they only vaped nicotine.

The CDC is urging everyone to stop using e-cigarettes, but several states are not waiting for federal officials to take stronger action.

Massachusetts this week became the first state to temporarily ban all retail and online sales of e-cigarettes. The ban is set to last for four months.

Other states have stopped the sale of flavored vaping products, saying the fruit and candy flavors appeal to young people.

The largest e-cigarette maker, JUUL, announced this week it will stop advertising its products.

E-cigarettes heat up liquid inside a cartridge and create a nicotine-filled vapor.

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Federal officials have ordered JUUL to stop marketing e-cigarettes as a safer alternative to smoking tobacco cigarettes, saying such claims have never been proved.

They also strongly recommend e-cigarettes users not go back to regular cigarettes and to seek help if they have trouble quitting smoking. (VOA)