A terror attack on Barcelona's subway system, thwarted by Spanish authorities, would have used two to four suicide bombers wearing explosive vests that were to be detonated simultaneously while another plotter detonated three to four more devices placed in the subway, investigative sources told ABC News.
News of the extremist Islamist plot became public over the weekend, and Wednesday a Spanish judge released additional details of the planned massacre, which sources now say appears to have been timed for this week's visit by Pakistani President Pervez Musharraf.
Fourteen plotters were arrested, and a large cache of bomb-making equipment and supplies were seized, including about 2 ounces of a nitro cellulous explosive, lead and steel ball bearings often used as shrapnel in anti-personnel suicide bombs, an empty box of Fontein Royal flares, pyrotechnics, four mechanical timers, wire cutters, other tools, detonator cable and a large amount of audio and printed material.
The investigation into the plot was dubbed operation "Cantata" by Spanish authorities, ABC has learned. "Cantata" roughly translates as "singing," a term cops often use to describe an informant giving them information about his cohorts.
Authorities are still hunting for additional members of the plot, which U.S. law enforcement and intelligence sources believe was credible. The plot was hatched in Pakistan, sources said, and believed to be al Qaeda-directed or inspired. The men had recently entered Spain from Pakistan.
Following the arrests this weekend, Spain's Interior Minister Alfredo Perez Rubalcaba said the group was actively preparing an attack and not just recruiting or financing.
"Here we are looking at something different: a well-organized group who were going beyond ideological radicalism to acquiring materials to make explosives and therefore eventually to carry out violent attacks," he said. He said a range of bomb-making materials and computers were also seized in the raids.
Four of the men arrested have been released, and 10 are still being held.
Word of the plot revived the nightmarish terror attack on Madrid's subway system March 11, 2004, that killed 191 commuters and wounded nearly 1,800.