Is there something going on with google image search?

Last few days there's something strange - looks like index rebuilding.
Noticed it on a site that had previously few thousand images indexed, and their numbers being less than 100 when checked few days ago. In the course of the next days it seems like they're getting back there.
Strange thing is that I see many gaps of missing images on very wide range of query spaces. Even on a very popular one like "news" - news - Google Search
The blank images' spots make me think that it's not just my site that has issues with image index, but there is something brewing. Image index crash/rebuild or similar.