While the American chocolate industry has already been accused of using child slaves to harvest cocoa, some newly filed class action lawsuits bring a new twist to the issue.

The suits were filed on Monday in California against Hershey, Nestle, and Mars, alleging the companies knowingly use cocoa harvested by child slaves in west Africa. Aside from requesting monetary damages for those who bought the companies' chocolate, plaintiffs want the candy packaging to say child slaves were involved.

The lawsuits reference an ongoing study by Tulane University financed by the U.S. Department of Labor, which estimates more than 4,000 children are forced to work on Ivory Coast cocoa plantations.

"To make matters worse," the complaint reads, "sometimes extremely poor people sell their own children into slavery for as little as $30. Children that are sometimes not even 10 years old carry huge sacks that are so big that they cause them serious physical harm."

Nestle, Mars, and Hershey's all denied the claims.

In a statement from a Hershey spokesman, the company's sustainable farmer training programs were cited, adding that the company "will invest another $400 million in the region by 2020 to reduce instances of inappropriate labor issues."

West Africa is home to two-thirds of the world's cocoa beans. The world-wide chocolate industry is worth $90 billion.