Starter Fuse Blew While Car Was Running

I was waiting for food with my car running and I came back to a car that had turned off and a chlorine-like smell. Blinkers and all that seemed to work fine but the car wasnt starting so I concluded it was the starter fuse. Turns out I was right and when I replaced the fuse the car started right when I put it in but then I also saw a ton of smoke coming from underneath the fuse box. I quickly pulled the fuse and it stopped. The fuse I replaced was the 15A AM2 "IGN" fuse, ignition system fuse. Any ideas what this could be?