An evaluation of nuclear waste storage tanks at the Hanford site in eastern Washington state indicates more of the newest tanks could be at risk of developing leaks.

The Tri-City Herald reports tank farm contractor Washington River Protection Solutions compared the chemistry of the waste inside the site's oldest double-shell tank to the newer tanks.

According to the Washington Department of Ecology, the evaluation findings suggest building more tanks to hold the 56 million gallons (212 million liters) of waste may be required.

U.S. Department of Energy officials say the findings do not mean the tanks are leaking or will leak, but steps are being taken to prevent deterioration.

The oldest double-shell tank was taken out of service after waste leaked over time in between the two shells.