Slo-mo video of the bright light illuminating the building just prior to the explosion.
Ammonium nitrate is the oxidizer.
Try harder.
https://en.wikipedia.org/wiki/Ammonium_nitrate
Heating or any ignition source may cause violent combustion or explosion.[18] Ammonium nitrate reacts with combustible and reducing materials as it is a strong oxidant. Although it is mainly used for fertilizer, it can be used for explosives. It was sometimes used to blast away earth to make farm ponds.[19][20] Ammonium nitrate is also used to modify the detonation rate of other explosives, such as trinitrotoluene in the form of amatol.
https://en.wikipedia.org/wiki/Ammonium_nitrate