The Investigation
According to the Egyptian government, the bombers were Palestinians who had tried to enter Israel to carry out attacks there but were unsuccessful. The mastermind, Iyad Saleh, recruited Egyptians and Bedouins to gain explosives to be used in the attacks. Beginning in March 2004, the bombers used washing machine timers, mobile phones and modified gas cylinders to build the bombs. They used TNT and old explosives found in the Sinai (as it was many times a war zone), which were purchased from Bedouins, to complete the bombs.
Egypt has said that Saleh and one of his aides, Suleiman Ahmed Saleh Flayfil, died in the Hilton blast, apparently because their bomb timer had run out too fast. Three Egyptians, Younes Mohammed Mahmoud, Osama al-Nakhlawi, and Mohammed Jaez Sabbah were sentenced to death in November 2006 for their roles in the blast. Egypt arrested up to 2,400 people following the attacks.
According to investigators, there is no strong link to al-Qaeda in the blasts.
Read more about this topic: 2004 Sinai Bombings