WASHINGTON (AP) _ Two soft-drink companies were sued Tuesday by parents concerned about the possibility of cancer-causing benzene in popular kids' drinks.

Attorneys filed class-action lawsuits against the companies in Massachusetts Superior Court and in Florida Circuit Court. They accused Polar Beverages and In Zone Brands of not taking steps to keep benzene from forming in the beverages known as BellyWashers.

Benzene, a chemical linked to leukemia, can form in soft drinks containing these ingredients: Vitamin C, also called ascorbic acid, and sodium or potassium benzoate.

The presence of those ingredients doesn't mean benzene is present. Scientists say factors such as heat or light exposure can trigger a reaction that forms benzene in the beverages.

``It's impossible for parents to know which soft drinks are safe and which contain cancer-causing benzene,'' said Timothy Newell, one of the plaintiffs.

The lawsuits alleged that independent laboratory tests found benzene at levels above the limit considered safe for drinking water in drinks made by Polar Beverages of Worcester, Mass., and In Zone Brands of Austell, Ga. The plaintiffs ask that companies be prevented from selling drinks that may contain benzene in Massachusetts and Florida.