Deletion of MRP area &1 is not possible

What causes this issue?

You would like to delete the MRP area &V1&, but this MRP area is of type
<ZK>plant</> (01).

System Response

You cannot delete MRP areas of type <ZK>plant</> (01).

How to fix this error?

If you have to delete an MRP area of type <ZK>plant</> (01), you first
have to delete the assigned plant.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.