Law firm McRoberts, Roberts & Rainer LLP have joined forces with a former state prosecutor to file class action lawsuits against In Zone Brands, who make Bellywashers drinks, and Polar Beverages.
The suits are the first to be filed amid recent concern over benzene contamination of soft drinks. Benzene is listed as a carcinogen by public health bodies.
The action comes two months after the US Food and Drug Administration (FDA) first revealed to BeverageDaily.com it had found some soft drinks contaminated with benzene above America's five parts per billion limit for drinking water.
The suspected source of the benzene is two common ingredients - sodium benzoate and ascorbic acid - in the drinks, although heat and light exposure has also been shown to increase benzene formation.
The lawyers, who have filed lawsuits in Boston and Tallahassee, released independent lab tests that reported one BellyWashers 2/3 Less Sugar drink with benzene several times higher than the World Health Organisation's (WHO) 10 parts per billion water limit.
The same lab found a Polar Diet Orange Dry drink containing benzene below this limit, but above the FDA's water limit.
The lawyers have called for the affected products to pulled from shop shelves.
Dr Tim Howard, a lawyer and veteran from litigation against tobacco firms, said: "Parents have a legal right to know if benzene is in their children's drinks. Responsible corporations must act to remove these lethal toxins that are so easily prevented."
Both the FDA and US soft drinks association have known for 15 years that benzene could form in soft drinks containing sodium benzoate and ascorbic acid. No public announcement was made.
The FDA has stressed that benzene levels it has found in recent testing of soft drinks did not pose an immediate health risk to consumers. It has not yet released the findings.
The agency re-opened its investigation into benzene in soft drinks last autumn, after it saw results from independent lab tests. These were commissioned by lawyer Ross Getman and Larry Alibrandi, a concerned food scientist, who worked on soft drinks industry testing for benzene in soft drinks back in 1990.
The lab tests, conducted in New York, found a Bellywashers drink and a Polar Diet Orange beverage containing benzene above the WHO tap water limit.
The American Beverage Association (ABA) has repeatedly assured that soft drinks were safe. It said people got more benzene from breathing the air around them every day. The ABA's chairman, Ralph Crowley Jr, is also head of Polar Beverages.