Storage cleaning

Hi everybody, we have a Centos 6 host with libvirtd 0.10.2. It's holding a storage pool of about 3.5 TB with 4 VMs. I decided to rearrange them, so I destroyed and undefined two of them. But now I am not able to install a new one because virsh gives me an "not enough space left". Those two undefined VMs still linger around somehow occupying a lot of that storage. How can I get rid of them? Name:           storage UUID:           8b25e085-38d8-5a09-f80f-a29150f25d42 Status:         laufend Persistent:     yes Automatischer Start: yes Kapazität:     3,54 TiB Zuordnung:      3,39 TiB Verfügbar:     155,27 GiB Thank you very much Lothar Schilling