[CuervO]

The actual GTA:SA fire is not possible to be handled in any way, it is not even synced for all players. The best thing you could do is to create burning explosions near the actual scripted fire, but even then extinguishing those fires is undetectable.

You can create a whole fire system by scripting but this would be pretty hard to do. Especially since there's no proper way to clear the native fire from a player's screen.