While experimenting with different things on my creative build, I lit a block of Netherrack. After lighting the block I decided I didn’t like the look, so I just mined the block of Netherrack. Once I mined the block I could still hear the fire burning and if I stood where the block of Netherrack was I started taking fire damage. So after a little more experimenting, I’ve discovered that if you place any block and light it with flint, then mine the block you can still hear the fire burning and it’s still capable of doing fire damage, but it’s invisible. You can’t see the fire. The only way you get can rid of the fire is by placing any block back down and then extinguishing the fire BEFORE you mine the block. As I was playing creative at the time, I thought it may be a glitch in just creative. However, I loaded up my survival world and was able to replicate the same thing in my survival. I don’t play multiplayer so I’m unsure if this can be replicated in multiplayer servers.