Crack in concrete/bitumen floor- damp smell?

[RAKing]

We have recently taken up carpet and underlay in a room in our house that has a really strong smell(damp/rubbery smell).

Can't see damp proof course so we think that must be the bitumen on top of the concrete but there's a 30cm crack in it that also has a dried watermark around the edge like there was a puddle there at one point. Pictures attached. Not damp now as far as we can tell (dehumidifiers in there dont collect much).

Any help on what to do from here? Cheers.

 

[Tigercubrider]

I believe that a liquid dpm could be added?
Either as a patch, or ideally the whole room?

 

[noseall]

We have recently taken up carpet and underlay in a room in our house that has a really strong smell(damp/rubbery smell).

I think you will get that same smell, having taken up a carpet in about 65% of UK houses.