Node.js and Socket.io memory leak fixing

In my multiplayer game we have just released an update using node.js and socket.io and we saw after some time that it has a memory leak.

I've read about Nodetime that it is a great program to check what is causing the memory leak. I have made two snapshots, but now I don't know what to do...

Those two snapshots are made with 8 minutes in between. Seeing that it already grow 16MB in Retainer > Other... I'm clueless what it could be. The count is also a very huge number. All those large instances are buffers, but I can't remember that I've used buffers myself, is it in socket.io?

Can someone enlighten me, or at least give some tips where to look?