Removing stains on vitrified tiles

[ddn]

Dear members,

We have purchased an unused (but 2 year old) apartment recently. The apartment has vitrified tiles for flooring. Unfortunately, some of the tiles have some stains. I have attached a picture for your reference.

We asked the cleaning staff to help us clean this stain and I am told that they tried their best to clean these stains (with soap solution and diluted acid). The surface of the tiles on the stain is as smooth as a new tile. Hence, this seems to be some sort of liquid stain, which has penetrated into the tile. I am not sure about this, as I am not very experienced in these matters. I was initially under the impression that vitrified tiles are non-porous and do not absorb anything. However, looking at this stain, I am confused on what could have caused such a stain.

I am stuck quite badly with this, as I don't think, I can find spare tiles. I would be grateful, if you could help me with the following doubts.

1. What is the best way to clean such stains? Is there any very good cleaning chemical? Or alternatively, are there some cleaning experts, whom I can consult for this?

2. Does anybody have any experience with such stains on tiles?

3. Any idea what could have caused such stains?


Thanks in advance,

Regards,
Dev