Federal regulators are threatening to pull e-cigarettes from shelves if manufacturers do not control teen use, which officials say has reached epidemic levels.

The Food and Drug Administration was prepared to embrace e-cigarettes as a way to wean adult smokers from cigarettes, but the agency is rethinking its approach after seeing scores of teens vaping. The crackdown by the FDA includes historic action against more than 1,300 retailers and five major manufacturers for their roles in "perpetuating youth access," the agency said. CNBC