Remove the 'files not found' entries ?

I had a Time Mchine 'tombstone' yesterday and have had to recover my iTunes library off a backup copy. As I don't have the TC back yet, I have rebuilt the iTunes library on a portable hard drive and its been re-importing the content from the backup onto the drive now for about four hours, and all is going well.

I had to create a new location for the library on the portable drive, and as the files are moved across, their entries are appearing, but the 'missing' entries are still there for the files which should have been on the TC library location. They have a little grey circle next to them with an exclamation mark - the 'original file not found' warning.

How do I get rid of these or is it just a case of manually deleting them ?