Mystery Water Appearing From Floor

[escaveloci 0]

hi,

I have an old apartment (about 30 years old) which the tenants just vacated.

I do not stay there but I drop by once in a while when the agent brings a prospective tenant for viewing.

I realised that in one of the bedroom, there's water gathering/forming in the middle of the room at 2 spots. this is rather strange to me as I cant figure out where and how it is from.

1. its not from the apartment upstairs as there's no leak in the ceiling

2. initially thought it might be the windows not being closed tight, but it is not. even if there's a crack in the glass or the joints aren't water tight, my curtains are dry and not wet at all.

the amount of water formed is quite a bit, its as if someone empty 0.5 to 1 litre of water at a location and it spreads out from there. I have to mop it up

my floor is tiled.

am clueless and honestly lost at what may be the source/cause. cant even get it fixed.

anyone with similar experience or thoughts?

by the way, I am not at the ground floor, so it can't be from the ground or the concrete slab water proofing.

TIA