I spilled some sauce in the oven, so I decided to clean it today.

I wiped the bottom and glass door, but the rest of the stuff was crusty and stuck to the bottom of the oven. I started the cycle and went about my business.

About 15 minutes later I hear a loud POP and saw little flames dancing at the bottom of the oven. I freak out, turn off the self-cleaning feature, grab the fire extinguisher and try to open the door, which wouldn't open.
I later found out this was a safety feature because the temperature inside was close to 480 °C (900 °F).

So, were these little dancing flames and the resulting smoke safe and normal in the operation of the self-clean cycle? If not, what can I do before running the cycle again to minimize flames and smoke?