Remove items from the Cluster Manager

Question

I have a clusterManager that contain items, and I want to remove these items every time that new items load. But what I get, is every time new items load, they're added to the previous ones. This happens even if I call these three lines:

mGoogleMap.clear();
mClusterManager.clearItems();
mClusterManager.cluster();

So what I want to achieve is to remove completely the previous items from my ClusterManager. What am I doing wrong?