Courtesy of capricornabhi (from another post - "Show Cause")
Subject: Absence from work without informing
Kind Attention: Mr. ABC (Project Engineer)
This has come to our notice that you are not coming to the office since 08.02.07 without informing your Department Head or any other person. Please show cause the reason for such prolonged absence. You are hereby requested to revert back to this letter either telephonically or personally within 15 days, failing which it will be presumed that you have nothing to say in this matter and disciplinary actions will be taken against you as per the company policy.
For (Company Name)
XYZ
I endorse this excellent response.
PALADIN