A sign warning of the presence of potentially harmful vapors is shown at the "C" tank farm during a media tour of the Hanford Nuclear Reservation Wednesday, July 9, 2014 near Richland, Wash. Officials... more 
A sign warning of the presence of potentially harmful vapors is shown at the "C" tank farm during a media tour of the Hanford Nuclear Reservation Wednesday, July 9, 2014 near Richland, Wash. Officials said Wednesday that 12,000 air samples taken at Hanford this year after more than three dozen workers reported being sickened by chemical vapors have failed to find a cause for the problem. (AP Photo/Ted S. Warren) less 
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Associated Press | Photo By Ted S. Warren
Wed, Jul 9, 2014 8:03 PM EDT