I cant tell you a great deal other than obviously with a huge disaster such as that the whole country knew very quickly. The govt. (PP-Aznar) first blamed ETA however several Marrocans were captured. I cant remember if Al-Q. accepted responsibility of not. The effect was an outcry and anger at Aznar for going to war and hence the PSOE won the elections. For more info visit
http://www.elpais.es or
http://www.elmundo.es and look for it. Theres tonnes of info, i hope you can read spanish though.