The Florida lawsuit alleges independent lab tests found Coca-Cola's Fanta Orange Pineapple contaminated with benzene at 4.7 times the five parts per billion limit for benzene in US drinking water.
A Cadbury Crush Pineapple drink is alleged to have contained benzene, a known carcinogen, at nearly 10 times this water limit.
The move by lawyers means that all three of America's top, branded soft drinks firms face class action lawsuits and possible court cases over alleged benzene in some of their drinks.
PepsiCo already faces class action lawsuits in three states - Massachusetts, Florida and California - following similar independent lab tests on its drinks.
The list of companies being sued has turned into a who's who of the US soft drinks industry. Others targeted include Kraft Foods, Ocean Spray Cranberries, Polar Beverages and In Zone Brands.
Concerns about benzene's presence in soft drinks have spread since the US Food and Drug Administration (FDA) revealed to BeverageDaily.com in February it had found some drinks containing benzene above the water limit.
The FDA confirmed on Friday it had found five such drinks, including Kraft's Crystal Light Sunrise Classic Orange, which contained benzene at more than 14 times the water limit. There is no specific limit set for soft drinks.
The agency again stressed there was no health risk for consumers, a message re-iterated by soft drinks firms.
But, the big players could face some sticky questions if the lawsuits filed against them make it to court.
That is because both the US soft drinks association and the FDA have known for 15 years about the suspected source of the benzene - a reaction between benzoate preservatives and ascorbic acid (vitamin C).
FDA and industry testing in late 1990 and early 1991 revealed the problem with these two common ingredients, a BeverageDaily.com investigation found.
No public announcement was made, and the FDA agreed to let the soft drinks firms privately "reformulate and get the word out", an FDA scientist there at the time said.
Now, the re-emergence of the issue and the lawsuits that have followed could examine this process in-depth, particularly because Cadbury Schweppes, Coca-Cola and PepsiCo were all part of the soft drinks association in 1990. Cadbury Schweppes was prominent in industry testing for benzene, a former employee claimed.
The Florida lawsuit says that these three firms, as well as Kraft Foods, should have known about the potential for benzene to form in drinks containing benzoates and vitamin C.
Kraft chemists were discussing the final formulation for its Crystal Light drink in December 1990, according to an internal company document passed to BeverageDaily.com. An internal FDA memo dated only days later described how soft drinks firms had approached it over the problem of benzene traces in drinks.
"It's now obvious that only a binding legal agreement will guarantee that the benzene goes and stays gone," said professor Richard Daynard, a lawyer and veteran from lawsuits against tobacco giants.
Still, doubts have emerged over the accuracy of testing for benzene in soft drinks, potentially jeopardising the lawsuits against drinks firms. And, FDA test results show not all drinks containing benzoate and vitamin C will contain benzene. Heat, especially, is considered a major factor in the reaction.
The FDA recently questioned the accuracy of its own off-the-shelf tests, after work by independent scientist James Neal-Kababick exposed a problem.
Kababick, who claimed to have devised a better test for benzene, said the FDA's procedure exposed drinks to heat, which could cause more benzene to form in the drink and so skew results.
It was unclear why the FDA had not looked into this over the last 15 years, despite conducting several spot checks for benzene in soft drinks.
Some beverage firms have taken no chances, however. The FDA said makers of affected soft drinks had all adjusted product formulas.
Kraft Foods said consumer safety was its top priority: "Kraft learned of this situation earlier this year and stopped producing and shipping Crystal Light Sunrise Orange single serve bottles in early February."
The group said it brought in an independent expert to help with reformulation and only resumed sales of the drink once benzene formation had been minimised. The FDA said it tested the new Crystal Light formulation and found less than one part per billion benzene.
Coca-Cola announced recently it was testing its soft drinks worldwide for benzene, but that its beverages were safe to consume.
See our related news (right) for more coverage of the benzene in soft drinks issue.