(NBC NEWS) -- Federal agents on Wednesday arrested a suspect in the mailing of
letters to President Barack Obama and a U.S. senator that initially
tested positive for the poison ricin.
The suspect was identified
as Paul Kevin Curtis of Tupelo, Miss., federal officials told NBC News.
They said he may appear in court as early as Wednesday night.
Both letters carried an identical closing statement, according to an FBI bulletin obtained by NBC News on Wednesday.
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 letter to Obama was intercepted at an off-site White House mail
facility and was being tested further, the FBI said. A federal law
enforcement official said that the letter was "very similar" to one
addressed to Sen. Roger Wicker, R-Miss. A third letter went to Sen. Carl
Two federal officials said late Wednesday that
an initial laboratory test on the material in the letters was
inconclusive. The test shows some level of ricin, they said, but the
potency is uncertain. They cannot tell whether the material is actually
harmful or not. So more tests have been ordered.
The sender of
the letters, one official said, "may have stumbled onto something," but
it's unknown if he actually made full-blown ricin toxin.
made from castor beans and can kill within 36 hours. There is no
antidote. Some threatening letters simply contain ground castor beans,
resulting in a positive field test for ricin without the concentrated
poison. Results from full laboratory tests are expected in the next 24
to 48 hours.
Filters at a second government mail screening facility also tested positive for ricin in preliminary screening Wednesday.
FBI official told NBC News that the agency did not initially believe
the letters were related to the attack on the Boston Marathon on Monday.
also for a time cleared the atrium of a Senate office building
Wednesday, removing suspicious envelopes and a package, before reopening
the offices. Capitol police were also investigating a suspicious
package at the office of Sen. Richard Shelby, R-Ala. Shelby's staff had
not been evacuated.
The Wicker letter had no return address. The
FBI confirmed the preliminary positive test on it Tuesday. That letter
was intercepted at a postal facility in Maryland that screens mail sent
to Congress, and never reached Wicker's office.
were made aware of the Wicker letter during a briefing Tuesday evening
on the bombing in Boston. Sen. Claire McCaskill, D-Mo., said that the
person who sent Wicker the letter writes often to elected officials.
can be exposed to ricin by touching a ricin-laced letter or by inhaling
particles that enter the air when the envelope is opened. Touching
ricin can cause a rash but is not usually fatal. Inhaling it can cause
trouble breathing, fever and other symptoms, and can be fatal.
hearing Wednesday on the Postal Service's finances, Postmaster General
Patrick Donahoe said that while there have been ricin scares in the
past, the recent discoveries were unprecedented.
been any actually proved that have gone through the system," Donahoe
said. "But we've got a process that we make sure that our employees know
-- We can actually track the mail back through the system to double
check from an employee health standpoint."
Field tests are
conducted anytime suspicious powder is found in a mail facility, and the
FBI cautioned that field tests and other preliminary tests can produce
inconsistent results. When tests show the possibility of a biological
agent, the material is sent to a laboratory for full analysis.
Windrem, Kasie Hunt, Kelly O'Donnell, Richard Esposito, Jeff Black,
Mike Viqueira and Dr. Kristina Krohn of NBC News contributed to this
By Pete Williams, Kristen Welker and Erin McClam, NBC News