I did not think stored ammonium nitrate would burn and detonate like that unless mixed with an accelerant.
It will under the right conditions.
Best example: The 1947 Texas City disaster was an industrial accident that occurred on April 16, 1947, in the Port of Texas City, Texas, at Galveston Bay. It was the deadliest industrial accident in U.S. history and one of history’s largest non-nuclear explosions. A mid-morning fire started on board the French-registered vessel SS Grandcamp (docked in the port) and detonated her cargo of about 2,300 tons (about 2,100 metric tons) of ammonium nitrate.