Federal authorities responded Tuesday to a report of a possible hazardous substance at a mail facility at Joint Base Anacostia-Bolling in the nation's capital, Lt. Col. Thomas F. Veale, a military spokesman, told CNN.
A potentially harmful substance was detected during a routine screening of incoming mail, Veale said.
Tests indicate it is a possible biotoxin, he said.
-- CNN's Carol Cratty and Greg Seaby contributed to this report.
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