Deleting Imported Accounts

I'm migrating from Salesforce to Zoho. I have migrated my leads with no problem. I migrated my accounts (18,000) and discovered that I omitted a couple of fields. I went to the Import History and selected "Undo this Import" for all of the imported accounts. However the accounts still appear in the database. How do I get rid of them. Can the Zoho DBA reset my account and let me start over?