Spanish officials concluded that the March 11, 2004, bombing of packed commuter trains in Madrid was an act of terrorism, likely motivated by Spain’s arrest of dozens of al Qaeda suspects after the September 11, 2001, attacks on the United States. (At least three of those arrested in Spain were charged with helping organize the 9/11 attacks.) On March 11, 2004, 10 backpacks loaded with dynamite exploded on four trains at the height of morning rush hour, killing 191 people and injuring 1,800. In the investigation that followed, officials uncovered other terrorist plots, including suicide bombings and assassinations aimed at interrupting Spain’s court system that tries terrorist suspects. The discoveries led officials to conclude that their nation had become a “crossroads” for Muslim extremists, in part because of Spain’s proximity to northern Africa. In April 2004, as authorities closed in on the hideout of the suspected Madrid bombing ringleader, a Tunisian man, and his associates, the suspects blew up their apartment. A total of 62 suspects were arrested in 2004 in association with the train bombing.