One week after the 9/11 attacks, a series of letters were sent to journalists and politicians in the USA. They contained the deadly biological agent Anthrax. The United States was gripped with fear as postal workers fell ill. The FBI launched one of the biggest and most expensive investigations in its history. In 2013 Rebecca Kesby spoke to Special Agent Scott Stanley about the case.

(Photo: Workers washing out rubbish bins. Credit: AP/Steve Mitchell)