However the Governor of Washington State, Jay Inslee, who said that 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.
"I met with Secretary Chu in Washington, DC, this afternoon, and he told me that the Department of Energy has now confirmed there are six tanks leaking radioactive waste at Hanford," Inslee said. Chu is US' Energy Secretary.
There are a total of 177 tanks at this site in Hanford, 149 of which are single-shell tanks.
"This is disturbing news for all Washingtonians. One week ago, Secretary Chu told me there was one tank leaking. But he told me today that his department did not adequately analyze data it had that would have shown the other tanks that are leaking," Inslee said.
"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," he said.
Hanford houses millions of gallons of radioactive waste left over from plutonium production for nuclear weapons.
It is considered one of the most contaminated sites on Earth, according to US government. .