More suspicious devices addressed to prominent Democrats — to New Jersey Sen. Cory Booker, California Sen. Kamala Harris and another to former intelligence chief James Clapper — were being investigated by law enforcement officials Friday.
The device addressed to Booker was intercepted in South Florida. The FBI confirmed that a suspicious package addressed to Booker had been recovered, adding that it was "similar in appearance" to at least 10 other packages this week addressed to high-profile Democrats and media figures.
Booker's office did not immediately respond to CNBC's requests for comment.
Separately, the New York Police Department said it removed a suspicious package from a U.S. Postal Service branch in midtown Manhattan that was "consistent" with the other suspected explosives. NBC News reported that the package was addressed to Clapper, who was the director of national intelligence during the Obama administration.
Later Friday morning, a man was arrested in Florida in connection with the ongoing investigation and is expected to face federal criminal charges, according to NBC News.
After the arrest of Florida resident Cesar Sayoc, 56, law enforcement officials told NBC that a similar package addressed to Harris was intercepted at a Sacramento postal facility.
White House press secretary Sarah Huckabee Sanders told reporters that "the president is receiving constant information as it is available." President Donald Trump, in a tweet Friday morning, said it was "very unfortunate" that the "'Bomb' stuff" has slowed the GOP's voting momentum ahead of the November midterm elections.
The White House did not immediately respond to CNBC's inquiries about the president's tweet.
Packages sent in manila envelopes and containing potentially explosive material have been addressed to former president Barack Obama, the New York residence of former president Bill Clinton and former Secretary of State Hillary Clinton, the New York office of news network CNN and actor Robert De Niro, among others.
De Niro, in a statement, said: "I thank God no one's been hurt, and I thank the brave and resourceful security and law enforcement people for protecting us. There's something more powerful than bombs, and that's your vote. People MUST vote!"
All of the targets of the suspected mail bombs have been either critical toward, or criticized by, the president. None of the packages discovered were detonated before being intercepted.
The president condemned the apparent mail bombing attempts as "egregious" and "abhorrent" conduct that has "no place in the United States" during a White House event earlier this week. But Trump also cast blame on the "hateful" media for causing "a very big part of the anger we see in our society."
The first device to be found was sent to the Bedford, New York, home of billionaire political donor George Soros, a pariah to the right wing, on Monday.
Two days later, the packages addressed to the Clintons and the Obamas were intercepted shortly before the Manhattan-based Time Warner Center, which houses CNN's offices, was evacuated. That device was addressed to former CIA Director John Brennan.
After Trump tweeted that the "Mainstream Media must clean up its act, FAST!" Brennan admonished him to "stop blaming others" in a tweet of his own.
Packages were also addressed to Rep. Maxine Waters, D-Calif., and former Attorney General Eric Holder. The latter device was redirected to the return address on the envelope, which was the Florida office of ex-Democratic National Committee Chair Debbie Wasserman Schultz, who is now a U.S. representative.
A suspicious package addressed to Vice President Joe Biden was also intercepted in Delaware, authorities reported Thursday.
In a press conference Thursday afternoon, New York political and law enforcement officials kept the lid on most details surrounding the ongoing investigation.
The suspected explosives were condemned across the political spectrum. But politicians of both major parties, as well as major media figures, differed sharply on what lessons to draw from the incidents.
"There is a total and complete lack of understanding at the White House about the seriousness of their continued attacks on the media," CNN President Jeff Zucker said in a statement. "The president, and especially the White House press secretary, should understand that their words matter. Thus far they have shown no comprehension of that."
Sanders pushed back in a tweet, saying Zucker "chose to attack and divide." And Trump, in a pre-dawn tweet of his own Friday, again went after CNN for "blaming me for the current spate of Bombs."
Asked by reporters on Thursday whether Trump bears any responsibility for the incidents as a result of comments he has made about his opponents — such as a recent remark lauding GOP Rep. Greg Gianforte for body slamming a reporter — Sanders said that "the president has condemned violence in all forms, has done that since day one and will continue to do that. But he certainly feels that everyone has a role to play."
This story is developing. Please check back for updates.