If all puddles have been removed, then a good (preferably dry) air flow will assist in lowering humidity.

If the water seeped in thru the walls, you can try a waterproofing treatment. If it came in thru a window - that's obvious then mate!

For plain concrete, an old fashioned fairly cheap (if you can locate it) treatment is 'water glass' - sodium silicate - it was used to help preserve eggs by coating the shells. It will soak in and chemically bond with the concrete. I seem to remember from my grandparents that it was traditional (even the chinese seemed to use it) Aussie egg treatment and was readily available, now possibly only from country hardware or specialist suppliers. You may track it down in an oriental supermarket - I don;t know if such traditions still carry on where you are.

I'm not an expert on the plaster, perhaps removing it, water glassing it (or some other soak-in treatment) and re-plastering? There will something you can use directly on the plaster. Many products now are bituminous, rubber, or silicone based - many just sit on the surface, and the water is still embedded in the wall, so will leak thru any crack in the treatment.

Robin