NPR Story
11:04 am
Thu April 18, 2013

Investigating Explosions And Chemical Threats

Originally published on Thu April 18, 2013 11:44 am

Explosions at the Boston Marathon, potentially ricin-laced letters intercepted en route to the White House and Sen. Roger Wicker, and an explosion at a fertilizer plant in Texas have each prompted investigations. In each case, authorities sift through evidence to construct a timeline of events.

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