Imagine there is a secret place deep underground where people go to dig out different things like gold or rocks. Sometimes, when they dig too deep, they might accidentally hit something hot or flammable. This can cause a fire to start down there, kind of like when you play with matches and the paper catches fire.
The problem is that the fire can't be put out easily because there's not much air down there for the firefighters to use their big hoses or buckets of water. The fire can also spread really quickly because there are lots of flammable things around like wood or oil.
When the fire keeps burning for a long time, it can create a lot of smoke that comes out of the entrance of the mine. This can be really dangerous for people who live nearby because they might breathe in the smoke, which can make them very sick. Sometimes the smoke is so bad that it can even be seen from far away.
People who work in the mine have to be very careful and wear special equipment to protect themselves from the fire and the smoke. They might even have to leave the mine for a while until the fire is put out.
Overall, a mine fire is a really big danger that can harm a lot of people and the environment around the mine. It's important to take precautions and prevent these kinds of accidents from happening in the first place.