At least six tanks containing radioactive waste in the US state of Washington are leaking, the state said Friday, urging more federal help to clean up a site used to make Cold War-era bombs.

Washington governor Jay Inslee said that the extent of the leaks at the Hanford site -- which first produced fuel for nuclear bombs in World War II and closed down 25 years ago -- was "disturbing."

"There is no immediate or near-term health risk associated with these newly discovered leaks, which are more than five miles from the Columbia River," he said, after meeting US Energy Secretary Steven Chu in Washington DC.

"But nonetheless this is disturbing news for all Washingtonians," he said.

He noted that Chu, the outgoing US energy secretary, told him a week ago that only one tank was leaking, but admitted "his department did not adequately analyze data it had that would have shown the other tanks that are leaking."

"This certainly raises serious questions about the integrity of all 149 single-shell tanks with radioactive liquid and sludge at Hanford.

"I believe we need a new system for removing waste from these aging tanks, and was heartened to hear that the Department of Energy is looking at options for accelerating that process."

The Hanford nuclear site, 185 miles (300 km) southeast of Seattle, was used to produce plutonium for the bomb that brought an end to World War II.

Output grew after 1945 to meet the challenges of the Cold War, but the last reactor closed down in 1987. Its website says: "Weapons production processes left solid and liquid wastes that posed a risk to the local environment."

Millions of gallons of leftover waste is contained in 177 tanks at the site, according to the Department of Energy, which in 1989 agreed a deal with Washington state authorities to clean up the Hanford Site.

Governor Inslee urged federal authorities to act quickly to ensure that looming US budget constraints to do not jeopardize extra measures for the nuclear waste site.

"Secretary Chu has a long-standing personal commitment to the clean-up of Hanford. He has assured me he will do all he can to address the issue of the leaking tanks," he said.

But he added: "Frankly, the state Department of Ecology is not convinced that current storage is adequate to meet legal and regulatory requirements.

"With potential sequestration and federal budget cuts looming, we need to be sure the federal government maintains its commitment and legal obligation to the cleanup of Hanford."

A Department of Energy spokesman, Lindsey Geisler, confirmed that "there are six tanks at the Hanford site .. including the one announced last week, that show declining levels of fluid."

"There is no immediate public health risk. The Department is working with the State of Washington and other key stakeholders to address the issues associated with these tanks," he added.

Details of exactly what kind of waste was involved were not immediately available.

A spokeswoman for governor Inslee, Jaime Smith, said: "It's nuclear waste. Different tanks have slightly different kinds of waste that they're holding. We're not clear yet on exactly what has been leaking for how long."

Washington state authorities hoped for more information about the leaking tanks soon, the spokeswoman told AFP.

"The Department of Energy has committed to try and get us more information pretty quickly, hopefully within the next week or so. So we should have more information soon," she said.