Firstly, Kulverstukas.. spasiba bolshoi... ochen horosho Informatsiya.
After looking at the recent UK pronouncement that this is indeed likely to be a bomb it seems that this conclusion was reached primarily from intercepted communications intelligence and/or human assets on the ground, and not the accident investigation team.
I think they may have forced Russia's hand here to come out and state what they know from the data they have in their possession... likely tomorrow morning.
Living in Moscow this is a HUGE story, and already people are baying for blood, so if proved don't expect any RoE to be adhered to, even loosely.