Yes it will. If there is sufficient quantity of ammonium nitrate, it can generate enough heat to catch fire and keep the fire going, without the need for an external catalyst such as a flame. As it burns, ammonium nitrate goes through chemical changes that lead to the production of oxygen, precisely what a fire needs to keep going and get bigger. As it heats up the chemical can fuse together, creating a seal or plug. The space behind the plug keeps on being heated and gases form. Hot gas expands, but, behind the plug, it has nowhere to go. Eventually, the gas will break through the seal and the force of that will trigger an explosion.