Cassandra - can't remove the nodes

I've accidently added new nodes to the test cluster. I removed the nodes afterwards but they still appear when connecting to the cluster.

The nodetool gossipinfo doesn't show them. The nodetool ring doesn't either but when connecting via the datastax Java client they do appear:

LOG4J 2015-05-06 15:44:54.796 INFO : [Cluster] - New Cassandra host /198.81.xxx.32 added LOG4J 2015-05-06 15:44:54.797 INFO : [Cluster] - New Cassandra host /198.81.xxx.31 added

How do I remove these nodes from the gossip cache/events, where do they come from?