What are these - Concrete mites?

[Poseidon]

My business has just moved into a new industrial unit and there are hundreds of these burrow holes all over the walls, all at various stages of burrow ranging from tiny to £2 coin size.

It looks like something has been burrowing out rather than in, occasionally there is a spider web like substance inside it when you break the top layer off.

Pictures below. Anyone know what theses are? Is the building away to fall down around me while I write this?;)

[TooLateForAName]

I'd be inclined to think cheap stty blocks that have flaked after painting.

But could be concrete worms I suppose.

try homes/diy ?