BOCA RATON, Fla.?Federal officials suspect that foul play rather than an environmental source is at the root of two Florida anthrax cases that have left one man dead and hundreds of co-workers being tested for the disease.

The FBI sealed off the offices of American Media Inc., where both men worked.

The Palm Beach County Health Department tested 743 people connected to the building Monday and expected 100 others Tuesday, said Alina Alonso, the department?s director of clinical services.

How the bacterium got into the newspaper?s office remained unknown. Federal investigators have eliminated the obvious environmental sources of anthrax, said Barbara Reynolds, a spokeswoman for the Centers for Disease Control and Prevention in Atlanta.

In Washington, Florida Sen. Bob Graham met with CDC Director Jeffrey Koplan.

?I asked Dr. Koplan what would be the likelihood that such a disease could have occurred without human intervention. His words were, ?Nil to none,?? Graham said.