Six tanks holding toxic, radioactive waste are leaking at the US government's Hanford site in Washington state.
That's five more than was reported earlier by the government, Bloomberg reported.
While the radioactive materials pose no immediate health risk, the leaks are renewing discussion over delays in emptying the aging tanks, according to The Associated Press.
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The underground storage tanks were installed decades ago, and were only intended to last about 20 years, Reuters reported.
"None of these tanks would be acceptable for use today. They are all beyond their design life. None of them should be in service," Tom Carpenter of Hanford Challenge, a Hanford watchdog group, told the AP. "And yet, they're holding two-thirds of the nation's high-level nuclear waste."
The 158-acre Hanford Nuclear Reservation is home to 177 of the tanks.
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Build between the 1940s and 1980s, they hold an estimated 53 million gallons of toxic, radioactive sludge that's so complex that the precise mix of ingredients isn't even known for most, the Seattle Times reported.
It is considered the most contaminated nuclear site in the US.
Federal officials told the AP they planned to work with Washington state to address the leaks.
Still, Sen. Ron Wyden, chairman of the Senate Energy and Natural Resources Committee, plans to ask for an investigation into Hanford's tank monitoring and maintenance program, according to the Seattle Times.