FBI makes arrest in suspected ricin-laced letters to Obama, U.S. senator

WASHINGTON (CNN) -- An arrest has been made in connection with possibly contaminated letters sent to President Obama and Sen. Roger Wicker, R-Miss., the Justice Department announced Wednesday.

Paul Kevin Curtis was arrested by the FBI at his home in Corinth, Miss., the department said in a statement.

Both letters carried an identical closing statement, according to an FBI bulletin.

According to the FBI bulletin, both letters, postmarked April 8, 2013, out of Memphis, Tenn., included an identical phrase, "to see a wrong and not expose it, is to become a silent partner to its continuance."

In addition, both letters are signed: "I am KC and I approve this message."

The letters were discovered Tuesday. The letters were stopped at a government mail-screening facility after initial tests indicated the presence of the poison ricin.

Because initial tests can be "inconsistent," the envelopes have been sent off for additional tests, an FBI statement said. The FBI does not expect to receive results from the tests until Thursday, federal law enforcement sources told CNN.