There's a long list of possibilities - and it's very difficult to tell what it is from a scan like that. A picture of the actual negative might help, but without that, there are a couple of things it might be - it could be digital noise from the minilab scanner, & subsequent interactions with the grain reduction & sharpening software features, it might be microscopic dust embedded in the negative that the Digital ICE system failed to catch, it could be a result of excessive humidity causing the backing paper to stick to the film - or quite a few others.
It would be useful to get an idea of what sort of storage conditions the film was kept in & what it was scanned on.
Also, if you can look at the negative under a high power loupe, that is probably the most useful way of starting the process of finding out what the culprit might be.