NEW YORK (AP) — Health officials say high schools students' use of electronic cigarettes tripled over three years.

In a large national survey last year, 4.5 percent of high school students said they had used an e-cigarette at least one day the previous month. That's up from 1.5 percent in 2011 and 2.8 percent in 2012.

It's not known how many only tried it once that month and didn't do it again.

E-cigarettes heat liquid nicotine into a vapor. Experts say nicotine is especially harmful to children. Dozens of states outlaw the sale of e-cigarettes to minors, and federal officials have proposed a nationwide ban on such sales.

The Centers for Disease Control and Prevention report Thursday also found 13 percent of high school students recently smoked regular cigarettes.

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