Such an explosion has happened before. A boatload of Ammonium Nitrate aboard a ship in the harbor in Galveston, Texas (April 16, 1947), also blew up, destroying a large part of the wharf and some nearby ships. It was probably the first time such a huge explosion was attributed to NH4NO3 (the chemical formula of Ammonium Nitrate), but its capability as a fast-reacting chemical was already known, as this is an ammonium analog to both saltpeter (used in early gunpowder) and potassium nitrate which is the ingredient in most modern “smokeless” gunpowders.
Another more recent one in the US was in April 2013, a fertilizer factory in West, TX. About 500k lbs of ammonium nitrate blew up, from an arson fire. Killed nearly 20 including most of town fire department.
There are some good videos on line of the aftermath of the Texas City disaster. It also destroyed a Monsanto factory, killed over 500 people, including all but one of Texas City’s fire department and even blew a small plane out of the sky.
Grand Champ exploded in Texas City about 100 yards from where I am siting right now. We are very aware of what we do and take safety as a part of our daily work. That does not sound strong enough. We take safety as the first consideration in everything we do. 1947 was a different era than today. But we would not have a warehouse full of ammonia nitrate in a populated area.