An investigation is under way into leaking nuclear waste storage tanks at a former atomic bomb-building facility in the north-western US state of Washington, reports said Saturday.
Governor Jay Inslee said there was no immediate health threat, but the level of leakage demanded action, according to CNN.
Of the 177 tanks at Hanford, 149 were built with a single-steel shell and are still in operation decades past their projected life span, the Seattle Times reported.
The investigation will determine whether more than just the six tanks are leaking.
The Department of Energy has an ongoing cleanup project at Hanford involving more than 53 million gallons (200 million litres) of radioactive and chemically hazardous waste and about 25 million cubic feet (750,000 cubic meters) of buried or stored solid waste, as well as spent nuclear fuel, and plutonium in various forms.
The leaks were discovered by Energy Department officials who found they had been inaccurately measuring the waste in the tanks. They concluded that the tanks had leaked anywhere from a few gallons to a few hundred gallons of radioactive material a year.
The underground tanks each hold tens of thousands of gallons of nuclear and chemical waste, the Seattle Times said. It quoted Suzanne Dahl, who oversees Hanford's tank-waste issues for the state, as saying it is too soon to say where the radioactive material has gone.
Dahl said it would take many years for the waste to work its way to the groundwater that moves toward the Columbia River 5 miles away.
"Is it held up directly underneath the tank farms? Is it moving? It's something we just don't know at this point," Dahl told the Times. "We do know that there is 150 to 200 feet of dry soil between the tanks and the groundwater."