FBI: Arrest made in ricin letters, suspicious packages not hazardous

A man in Mississippi has been arrested for allegedly sending letters laced with suspected ricin poison to President Barack Obama and other leaders in Washington D.C., according to the Associated Press.

FBI Special Agent in Charge Daniel McMullen said the man was arrested Wednesday in Tupelo, the AP reports. The FBI identified the suspect as Paul Kevin Curtis, 45, of Corinth, Miss.

6:38 p.m. update:

Capitol police say it turns out the suspicious packages investigated in the U.S. Senate on Wednesday weren't hazardous, according to the Associated Press.

But spokeswoman Makema Turner said a man was still being questioned late in the day after being stopped in connection with the packages, the AP reports.

From earlier:

Authorities are investigating suspicious letters sent to President Obama and multiple U.S. senators.

Suspicious letters to Obama and one senator were detected at government mail facilities. Other suspicious packages were reported at the U.S. Capitol and offices in senators' home states.

The Secret Service intercepted a letter to Obama that contained a suspicious substance. Initial tests show the substance is ricin, the same potentially fatal poison that was in a letter delivered to Mississippi Sen. Roger Wicker this week, according to the FBI.

Both letters reportedly contain the same language. CNN and other news outlets reported that the letters say: "To see a wrong and not expose it, is to become a silent partner to its continuance." The letters are also both signed: "I am KC and I approve this message."

The FBI says the letter to Obama was discovered at an off-site mail-screening facility.

There is "no indication" the letter is connected to Monday's bombing at the Boston Marathon, the FBI said in a statement.

A bomb squad was called to the Capitol building this morning and parts of some buildings were closed while authorities investigated.

Politico reports that emails to staffers say a suspicious package was discovered in the Hart Building and an envelope was found in a third-floor office. Police also responded to the third-floor in the Russell building, according to Politico.

Also today, Michigan Sen. Carl Levin said in a statement that a staffer at his Saginaw regional office received a suspicous-looking letter. The letter wasn't opened and authorities are now investigating. It isn't yet known whether the letter contained a threatening substance.

And the Phoenix office of Sen. Jeff Flake was evacuated after reports of suspicious packages this morning, the Arizona Republic reported. It wasn't immediately clear what made the packages suspicious or what they contained.

No one has been harmed in any of the incidents.

The suspicious letters sent to both Obama and Wicker were detected at off-site facilities that are not in close proximity to the White House or Capitol. Further testing is being done on both letters.

Mail to the president and lawmakers is processed at such facilities "to mitigate any risk," White House spokesman Jay Carney said this afternoon.

Sen. Claire McCaskill told reporters that investigators had a suspect in mind in connection with the letter sent to Wicker. Authorities have not announced any arrests in the case.

Ricin is a highly toxic substance that comes from castor beans, according to the Centers for Disease Control and Prevention. The beans can safely be made into castor oil. Ricin can be made from waste material from processing the beans. It can be a powder, mist or pellet, or dissolved in water.

In 2004, the AP described the substance as "twice as deadly as cobra venom."