The FBI says lab-tests have confirmed the presence of rice-in  in letters mailed to a President Barack Obama and a U.S. senator.

The FBI said today that further tests are still being conducted  but that lab results show the toxin was used in the mailings.

There are no known illnesses from the exposure.

Paul Kevin Curtis  is suspected of sending the letters to Obama and U.S. Sen. Roger Wicker.

He appeared in federal court Thursday on charges of threatening Obama and others, but he did not enter a plea.

His attorney said that the arrest was surprising and that Curtis maintains that he is innocent.