Thanks a lot for all ur replies.
I think one can start working.This is an extract from I-9 document Section 2
http://uscis.gov/graphics/formsfee/forms/files/i-9.pdf
Section 2 - Employer. For the purpose of completing this
For more detailed information, you may refer to the INS
Handbook for Employers, (Form M-274). You may obtain
the handbook at your local INS office.
Employers must complete Section 2 by examining evidence of
identity and employment eligibility within three (3) business
days of the date employment begins. If employees are
authorized to work, but are unable to present the required
document(s) within three business days, they must present a
receipt for the application of the document(s) within three
business days and the actual document(s) within ninety (90)
days