Health groups are calling on the US FDA to investigate the therapeutic claims electronic cigarette manufacturers are allegedly making in reference to their products.

The American Cancer Society’s Cancer Action Network, the American Lung Association, the American Heart Association, the Campaign for Tobacco-Free Kids and Truth Initiative sent a letter to Janet Woodcock, the director of FDA’s Center for Drug Evaluation and Research, calling for action last week.

The groups said Truth in Advertising reviewed more than 150 manufacturer and seller websites and found claims that e-cigarettes helped smokers stop smoking. To make these claims, the groups said FDA has to sign off on them first.