Wal-Mart, the nation's largest retailer, will retrain employees about its cigarette sales policy after the store was found to be one of the top 10 violators of federal regulations prohibiting tobacco sales to minors.

"We take this matter seriously. We are a leading supporter of children's health issues and we are going to retrain all associates and management to make sure they clearly understand the policy," said Wal-Mart spokesperson Jessica Moser.

Underage testers in North Carolina working with the U.S. Food and Drug Administration and the North Carolina Division of Alcohol Law Enforcement bought cigarettes at Wal-Mart 44% of the time.

The top violator was Ingles Markets, where testers were sold cigarettes 84% of the time. Other top violators include Phar-Mor, CVS, Eckerd's, Wilco, K-Mart, Food Lion, Bi-Lo, Pantry Convenience stores, Winn-Dixie, Kerr, Piggly Wiggly and Harris Teeter.

All of the companies said that it was not their policy to sell tobacco to minors.