The company's corporate media affairs department at 120 Park Avenue received an envelope containing a white powder.
According to a recorded message at Philip Morris' toll-free security number, all employees on that floor have been tested for anthrax exposure and given prescriptions for the antibiotic Cipro as a precaution, although no results have come back yet.
The company expects to have test results no later than Sunday evening, and encouraged employees to call the security phone number over the weekend to see if the building will reopen on Monday.
Also as a precaution, the building's ventilation system was shut down and the hazardous materials unit of the New York Police Department examined and cleaned the building. The suspicious envelope is being tested by the New York Department of Health.
Philip Morris' 100 Park Avenue location remained open today and operated under normal business hours.
The media affairs department could not be reached for comment.