On 26 February 1993, a bomb exploded in the lower levels of the World Trade Center. The blast caused minor damage to the building’s foundation but it resulted in six deaths and 1000 injuries.
Richert, Lucas Paul. "World Trade Center terrorist bomb attack". The Literary Encyclopedia. First published 01 October 2008
[http://www.litencyc.com/php/stopics.php?rec=true&UID=3965, accessed 16 April 2014.]