There are some strange noises coming out of the cave.

I own a property about 2 hours outside of a major city here in Australia (Victoria). Id rather not say the name of the nearest small town.
Its only about 120 hectares but one of the things that attracted me to the block was its clean bore water, small creek and rocky mounds. Huge boulders break out of the ground all over the place, some forming pretty big structures. I guess thats why I got it pretty cheap, since its not ideal for farming because of them.
On the site is a small house, more like a shack with 2 bedrooms a fire place, basic kitchen but no electricity.
Three weeks ago I went exploring and was surprised to find an opening in between 2 large rocks that formed a cave. I thought it was just shallow till I went in. This thing is huge! It slopes down at a gentle gradient for about 10 meters then drops sharply. I didnt have a torch with me at the time, so I left it for another time.
Four days later I returned with a maglight and was surprised in what I found. The cave drops about 30 meters then there is a sharp turn to the right. I cant see past the turn.
As I was about to return to the shack to grab some rope, I heard a sound that I can only describe as metal scraping on rock face. Long scrapes each time. This freaked me out abit, but the thing that really got me was the flashes of light. Every once in a while, a flash of light would go off, like a camera flash. Then the scraping would begin.
I screamed out incase it was miners or kids. The scraping would stop, but the flashes would become more frequent...then the scraping would begin again.
I dont know what to do. I contacted the council and they have no records of mining in that area.
I think I need to go down and have a look for myself.
Any ideas?