An investigation continues into why radioactive waste appears to have leaked into site soil at Washington state's Hanford Nuclear Reservation.
Inspectors detected higher radioactivity levels under tank AY-102 during a routine inspection on June 20, 2013.
Washington Gov. Jay Inslee said in a June 21, 2013 statement to media that the situation "must be treated with the utmost seriousness."
State and federal officials have long said leaking tanks at Hanford do not pose an immediate threat to the environment or public health.
The AY-102 tank is one of several at the facility in use beyond their intended life span. The Energy Department announced in 2012 that AY-102 was leaking between its two walls, but reported then that no waste had escaped.