FBI identifies suspect in ricin letters as Paul Kevin Curtis 45 year old - Mississippi.
A suspect was arrested Wednesday in connection with the mailing of two letters containing poison to President Barack Obama and Mississippi Sen. Roger Wicker, a law enforcement source said.
Both letters were intercepted, the contents were tested, and were found to contain the substance ricin.

Both letters were postmarked April 8 from Memphis and appear to be from the same individual, according to the FBI.

Each letter said 'to see a wrong and not expose it is to become a silent partner to its continuance.'

Each was signed 'I am KC and I approve this message.'

The arrest was made by a joint by a joint FBI and Capitol Police Task Force.

U.S. official confirms there is an arrest in the investigation of recent mailings of ricin to federal officials, CBS News correspondent Bob Orr reported.

Earlier, a third suspicious letter discovered this week -- this one addressed to Obama -- has been intercepted and is being tested for the poisonous substance ricin.

Threatening letters to the president and congressional leaders are not unusual -- their mail is processed at a facility about 10 miles outside of Washington in Landover, Md. The current security protocols -- which seem to be working exactly as they were set to do -- were put in place after the 2001 anthrax scar.