Luke Bryan is one of 45 celebrities who recently received letters from the Federal Trade Commission regarding improper promotion of products on Instagram. The country superstar and the other artists, actors and celebrities have been using the social media platform to advertise products without disclosing their potential financial gains.

Billboard reports that the FTC sent out their letters after receiving complaints from Public Citizen, Campaign for a Commercial-Free Childhood and the Center for Digital Democracy. The three advocacy groups claim that Instagram “has become a platform for disguised advertising directed towards young consumers" and requested that the FTC enforce the laws that require "influencers" to explain their ties to the products they're promoting.

Also among those sent letters by the FTC are Jamie Lynn Spears, Lindsay Lohan, Lucy Hale, Akon, Jennifer Lopez and more. The FTC sent the letters to educate, not publish, those involved, the organization says.

All of Luke Bryan's Singles, Ranked

The FTC's letters to Bryan and the other celebrities were made public on May 4, after Womens Wear Daily filed a Freedom of Information Act request. Each letter explains the FTC's Endorsement Guides, which "state that if there is a ‘material connection’ between the endorser and the marketer of a product -- in other words, a connection that might affect the weight or credibility that consumers give the endorsement -- that connection should be clearly and conspicuously disclosed, unless the connection is already clear from the context of the communication containing the endorsement."

The specific Instagram post named in Bryan's letter from the FTC has to do with his ties to Cabela's, the retail chain that sells gear for outdoor sports, including hunting and fishing. Bryan's HFE clothing line -- named for his single "Huntin', Fishin' and Lovin' Every Day" -- is available at the store, and he often mentions the line's products on his Instagram account. Although the specific Instagram post mentioned in the FTC's letters to Bryan and Cabela's has been removed, others remain on Bryan's Instagram page, marked with the "#sponsor" hashtag.

Country Music's Nastiest Lawsuits

How Well Do You REALLY Know Luke Bryan?