The evidence so far: On the evening of the bombings, a white Renault van is discovered outside the station where the terrorists are believed to have put the bags containing the bombs on the commuter trains.
Inside the van police found traces of explosives, seven copper detonators, a bag containing items of clothing, and an audio tape in Arabic with verses of the Koran.
• The London-based Al-Quds al Arabi newspaper receives an e-mail on Thursday evening with an alleged confession from Abu Hafs al-Masri Brigades which said it is part of al-Qaeda.
• A bag is found at one of the train wrecks with an unexploded bomb and a mobile phone which leads to the arrests on Saturday evening of three Moroccans and two Indians.
• On Saturday night, Madrid police are led to a video tape left in a waste bin near the largest Madrid mosque claiming the Madrid bombings. "It is our response to your collaboration with the criminal Bush and his allies. There will be more if Allah wills it. You love life, we love death."