The Food and Drug Administration issued warning letters to the makers of Winston, Natural Spirit and Nat Sherman cigarettes over their "additive-free" and "natural" label claims.

The agency issued the warnings to ITG Brands LLC, Santa Fe Natural Tobacco Company Inc. and Sherman's 1400 Broadway N.Y.C. Ltd. The issue over the claims is that they may lead consumers to believe the products pose a lower risk. That claim has to be scientifically proven.

The warning letters come several days after a large group of anti-tobacco organizations sent the FDA a letter urging the agency to enforce marketing regulations against Santa Fe Natural Tobacco over the marketing claims.

There was no immediate response from the companies.