How to delete the obsolete webdynpro interface IWCI* file

hi:

I created a local webdyrnpro component ZZ_TEST, and then I deleted this webdynpro, but I found that its corresponding interface file ZIWCI_ZTEST still existed in system.

And when I tried to delete it manually, the following message is displayed:

'Object cannot be edited with Class Builder'.

and this interface could not be edited or renamed too. So it is leaved in system foreever and I have no way to delete it, which block me to recreate webdynrpo component ZZ_TEST.

So, do you have any good way to force to delete this interface clearly?

thanks.