How delete Sales Lead in Bulk

Summary:

I want to delete all the Sales Leads in bulk, in the test environment I first exported all the Leads and with the import activity I deleted them with the Lead Identifier.

In the productive environment I did exactly the same, but when I do the import activity to remove records none of them are removed and I get the error "The data couldn't be imported. Details: Rows cannot be removed from entity MklLeadVO_20259902..."

How can I remove all the Sales Leads? My user in test and in production have the same roles.

PS: We need to remove all Leads because an update will be made to all records.