They are unrelated to a larger litigation going on in Ecuador, which seeks $6 billion in damages from the US oil company on charges it contaminated the rain forest from 1972 to 1992. Chevron denies the claims.

Gloria Chamba, a plaintiff in the case, had alleged that Chevron pollution had given her son leukemia. But she admitted during deposition her son never had the disease.

Similarly, Luisa Gonzales said at her deposition that she had never been diagnosed with breast cancer. A related suit by her husband was also dismissed.

"In our mind, this reflects the kind and quality of allegations being made against us," said Chevron spokesman Don Campbell.

Steven Donziger, a lawyer who represents 30,000 Ecuadorean jungle dwellers suing Chevron for $6 billion, said this ruling will not affect their case in an Ecuadorean court.

"We are only suing for clean up costs, while the San Francisco case is about health impact on individuals," Donziger said. "Chevron is using their public relations spin against the thousands of legitimate Ecuadorean victims of their policies."

Judge William Alsup of the US District Court for the Northern District of California, brought up the possibility of misconduct by the plaintiff's lawyers in his ruling handed down Friday.

"It is clear to the Court that this case was manufactured by plaintiffs' counsel for reasons other than to seek a recovery on these plaintiffs' behalf," he wrote. "This litigation is likely a smaller piece of some larger scheme against defendants."

The plaintiffs' attorneys could not be immediately reached for comment.