The ammonium nitrate part of the story is very believable.
What caused it to go off is the question that needs answer.
Something had to trigger it........................
I’ve also heard Sodium Nitrate.
That can’t be as it would need a fuel to go with it.
Ammonium nitrate has fuel and oxidizer in the same package.
Ammonium nitrate makes more sense.
“Something had to trigger it”
Wikipedia indicates the tons of ammonium nitrate must have been a mixture which was intentionally created to make it an explosive.
So yes, I think the explosive mixture needed a detonator to make them explode, so there was a trigger other than a simple flame.
The ammonium nitrate mixtures are good commercial explosives partly because they are safe unless used with a detonator.
You mean, like a drone-fired missile?
Fire can absolutely trigger it under the right circumstances. It has happened in multiple ammonium nitrate explosions over the years, such as the West, TX explosion from a few years ago.