Audit log cleaning from AuditData table

Hi,

I had requirement to clean up the audit logs from AuditData table of all the content DB's.

I have one web application with more then 300 site collection in it which are organized in more then 10 content DB's.

Now to remove the audit logs , i am utilizing below powershell script as suggested by msdn.

$site = Get-SPSite URL
$Site.Audit.DeleteEntries($date) 

But i obseved that , there were some site collections which were not saving audit logs into there respective content DB's.

But when i checked the audit logs with respect to those site collection, i found all related audit logs into a different content DB. Which were not getting deleted through above powershell because above command get execute for mapped content DB.

Can someone please suggest , if it is possible to delete the Audit data based on site collection as well as content database ?

Or what could be the reason for this content DB mismatching.

Please let me know for any query.

Regards:

Sanjay