The chemicals called PCBs that have been in the Hudson River for decades are apparently leaching into the water, not becoming harmlessly imbedded in the silt on the bottom, federal environmental regulators said.

The finding, released Thursday, could bolster calls for the General Electric Co. to pay millions of dollars for dredging along the river to remove the suspected cancer-causing chemicals.Analysis of samples of Hudson River silt taken in 1994 show that the level of PCBs in the silt was roughly 30 percent lower then than it was 10 years earlier. That suggests the chemicals have been dispersed downstream by the flow of the river, officials at the federal Environmental Protection Agency said.

"The fact that these PCBs are so rapidly re-entering the river system is startling," the EPA's New York regional administrator, Jeanne Fox, said.

But General Electric attacked the veracity of the results, saying the EPA was using the data to move closer to a "preordained, politically motivated dredging solution" throughout the Hudson.