Emptying trash containing locked back-ups from Trash

I deleted older back-ups from my Time Machine external drive. The deletions ended up in the trash. Now I have two documents, boot.efi and BootX, that I cannot seem to empty from the trash. Icons of the documents have a padlock next to them. When I try to unlock by clicking on Get Info the "locked" selection is grayed out. How do I get this "trash" to empty?