Doug Hamilton of Louisville's emergency management agency said Friday that the evacuation of an area 1.2 miles around the site will remain in place indefinitely.
The fire that started Wednesday continues to burn. Officials said they are letting the chemical blaze burn while they undertake the difficult task of moving a dozen derailed cars away from the flaming tanker.
Of particular concern are two tankers closest to the fire that contain dangerous hydrogen fluoride.
Art Smith of the U.S. Environmental Protection Agency says water and air samples continue to show there are no immediate concerns about contamination.
(Copyright 2012 by The Associated Press. All Rights Reserved.)