There has been a lot made of two controlled explosions that the police organised at the bus bomb site. These were very likely precautionary measures to open suspicious parcels that were found (the polic have stated this). In the early days the explosives were thought to be military or construction grade high explosives rather than the mixture we are now told it was. That required both more room and a greater weight of explosive so the possibility of the "bus bomber" carrying more than one is unlikely.

I remember hearing at least one report that a timing device had been found embedded in the remains of one of the bombers. I think that was the bus and the forensic examination is obviously going to be long - he was identified as being on the bus as his description matched that of a head found at the scene.