Removing blueprint gone wrong?

Hi

I have been using blueprints from the public forum on my server, and untill today it has been going fine.

Occasionally when I use undoblueprint, a 'mirage' is left behind, like a picture remains of the building.
But if i log out and in again it is gone.

Except for today.

Part of the building was still there when i logged on, now solid.
Is there any way to remove it quickly?
Console command or similar?

I tried tearing it down and using tnt, but tnt is not very effective.
Tearing it down manually takes forever. There are thousands of elements.

Any ideas?

Thanks avanar I will try that