Changing item from no batch tracking to enabling batch tracking

I have a few items that were originally set up having no batch tracking enabled. I removed all inventory and demand for these items. I tried to change the tracking from no tracking to batch tracking and it will not let me change as it says there is inventory of these items in the system. However Looking at the item there is no inventory. I am assuming there is maybe a .0001 of inventory and it does not show up visibly. Any ideas how to solve this without creating new item numbers for these items. Jim