Other day, we noticed a huge bubble in the ceiling of our study room downstairs. Called the plumber. He cut open the dry wall in the ceiling. And concluded that it is not the drain or any pipeline that is leaking. It is something to do with the leakage from the tiles in the shower stall directly above. Can you please help?

If it is the shower pan that's leaking it's a big issue. What can you tell us about the materials used to build the pan, is it ceramic or what