Alert - Receive two email notification,

Dear All

i create Alert to send one email notification to fixed email when requisition approved, but i always receive two email notification when requisition approved.

it is event based, from table PO_REQUISITION_HEADERS_ALL

the select statment

select prh.SEGMENT1

INTO &APPROV

from po_requisition_headers_all   prh

where prh.ROWID = :ROWID

and prh.AUTHORIZATION_STATUS='APPROVED';

please advise