Carried-foward PO; budget issue

Hi Experts,

We have successfully carry forward one PO along with its budget and while checking the same in FMIOI table it is showing that system has successfully carried forward it in 2015 i.e. status 31.

Now when am trying to delete this PO system is giving budget error.

Logically system should release the budget but instead system is asking for budget.

No other activity has been carried out in that budget address and PR & PO valuation is same.

Please suggest

Regards

Sarvottam