WASHINGTON - A suspect was charged on Thursday for using mail to threaten President Barack Obama and two others.

The suspect, Paul Kevin Curtis, now faces as many as 15 years in prison, three years supervised release, and a fine of 500,000 dollars under the federal charges, announced U.S. Attorney for the Northern District of Mississippi and the FBI on Thursday.

He is charged with sending mail "containing threats to take the life of or to inflict bodily harm upon the President of the United States" and also sending mail "containing a threat to injure the person of others."

Curtis was arrested Wednesday evening at his resident in Corinth, Mississippi, following investigation to suspicious letters addressed to Obama, a Senator and a local official in Mississippi.

The suspicious letters addressed to Obama and Senator Roger Wicker were intercepted at off-site mail facilities for the White House and the Capitol Hill respectively and both tested positive for ricin, a highly toxic substance.

The incidents came one day after two explosions occurred near the finish line of the Boston Marathon, killing three people and wounding over 170 others. But the authorities have not found a link to Monday's Boston bombings.