Pipe bombs were sent to several prominent Democrats, including former President Barack Obama and former Secretary of State Hillary Clinton, setting off an intense investigation on Wednesday into whether a bomber is going after political figures vilified by the right wing.
CNN received a similar bomb, addressed to John O. Brennan, a career intelligence officer who served as Mr. Obama’s C.I.A. director. The discovery of the device caused a mass evacuation of the Time Warner Center in Midtown Manhattan, where the network is located.
None of the devices harmed anyone; it was not immediately clear whether any of them could have exploded. One law enforcement official said investigators were examining the possibility that they were hoax devices.
The F.B.I. said in a statement that the devices were similar to one found Monday at the home of George Soros, the billionaire philanthropist and liberal donor. Investigators were seeking to determine whether they were sent by the same person or persons.
Coming less than two weeks before the midterm elections, the discovery of the pipe bombs reverberated across a country already on edge, stirring anew questions about whether political discourse had grown too vitriolic.
Mrs. Clinton, Mr. Obama, Mr. Soros and CNN have all figured prominently in conservative political attacks — many of which have been led by President Trump. He has often referred to major news organizations as “the enemy of the people,” and has shown contempt for CNN.
Mr. Trump, speaking at the White House, called the attempted bombings “despicable acts.”
“In these times, we have to unify, we have to come together,” he said.
The device sent to CNN was addressed to Mr. Brennan, a Republican and a harsh critic of Mr. Trump. The president revoked his security clearance in what was seen as an act of retribution.
All the packages were mailed in manila envelopes lined with Bubble Wrap and bearing return addresses with the name of Debbie Wasserman Schultz, a Florida congresswoman and a former Democratic National Committee chairwoman, the F.B.I. said. The mailing labels were computer-printed and six first-class stamps were affixed to all of the envelopes.
A fifth device sent to Mr. Obama’s attorney general, Eric H. Holder Jr., was apparently misaddressed, and because Ms. Wasserman Schultz’s name was on the return address, it was ultimately delivered to her district office in Florida, the F.B.I. said.
Another package addressed to a Democrat, Representative Maxine Waters of California, was intercepted at a Congressional mail facility, Ms. Waters said in a statement. In recent months, Mr. Trump and Ms. Waters have often ridiculed each another.
The one sent to CNN’s offices was delivered by courier, a law enforcement official said. However, it also had half-a-dozen first-class postage stamps on it. Investigators believe the bomb sent to Mr. Soros’s home was dropped off in his mailbox.
Mrs. Clinton, in an address to a crowd of about 200 Democratic donors in Florida on Wednesday, said: “It is a troubling time, isn’t it, and it’s a time of deep divisions and we have to do everything we can to bring our country together.”
In Manhattan, Mayor Bill de Blasio called the attempted bombings “an effort to terrorize” and vowed the city’s residents “won’t allow terrorism to change us.”
The device addressed to Mrs. Clinton in Westchester County, north of New York City, was found late Tuesday by a Secret Service employee who screens mail for her, the statement said. The package addressed to Mr. Obama was intercepted early Wednesday by Secret Service personnel in Washington.
Shortly after the Secret Service made that announcement, the Time Warner Center, a major office complex, was evacuated when a similar device was discovered to have been sent to CNN’s offices there.
A senior law enforcement official in New York, describing the bomb sent to CNN, said it was intercepted in the basement mailroom and resembled the others: “Same package. Same device.”
That device was constructed from a length of pipe a little longer than six inches and wrapped in black tape with what appeared to be epoxy on the ends, according to a person who had seen a photograph of it.
What could be a timer was attached to the side of the pipe, and wires were visible at both ends.
Like the bomb sent to Mr. Soros’s home, the envelope it arrived in was roughly 5 by 8 inches and had a printed white address label and half-a-dozen first-class postage stamps affixed to the outside.
On Wednesday afternoon, New York City’s police commissioner, James P. O’Neill, said that the CNN bomb was “a live explosive device” and that it would be rendered harmless and sent to the F.B.I. to be analyzed. The package that contained the device also included white powder that the police were testing to determine if it is toxic, he said.
Some bomb technicians who studied photos of the device that circulated on social media suggested that the bomb sent to CNN had hallmarks of fake explosives — the kind more typically depicted on television and in movies, rather than devices capable of detonating.
An LCD clock was taped to the middle of the pipe, a feature that experts say is typically shown on fictional bombs in an attempt to ratchet up dramatic tension, but unnecessary in real life.
In fact, bombmakers generally avoid attaching visible clocks to their devices to keep from tipping off their targets about when the bombs are set to explode.
One of the envelopes that contained a device had more postage than needed to be delivered, according to a former law enforcement official briefed on the investigation.
The extra postage led investigators to believe that the person who mailed it wanted to avoid going to a post office to buy the correct postage — a step to evade detection, the official said.
F.B.I. Director Christopher A. Wray said in a statement: “This investigation is of the highest priority for the F.B.I. We have committed the full strength of the F.B.I.’s resources and, together with our partners on our Joint Terrorism Task Forces, we will continue to work to identify and arrest whoever is responsible for sending these packages.”
Early this month, federal authorities said they intercepted multiple packages suspected of containing the lethal substance ricin, addressed to President Trump and at least two top Pentagon officials. In February, an envelope containing a white powdery substance that investigators later determined was cornstarch was sent to the Manhattan apartment of Donald Trump Jr.’s mother-in-law.
Bomb technicians will seek to determine where the bombs’ components were purchased or the bombs were made. Evidence technicians will attempt to recover traces of DNA or fingerprints from the components and the envelopes that contained the bombs.
Federal agents with the United States Postal Inspection Service could play an important role in the investigation if any of the packages were delivered through the mail.
They would examine the postage and postmarks and seek to determine where the envelopes were mailed from. Investigators could examine surveillance video at post offices and around blue letter boxes where the packages may have been deposited.
It is unclear where exactly the package addressed to Mrs. Clinton was sent. A security guard at the Clinton Foundation’s Midtown Manhattan offices said the explosive device was addressed to Mrs. Clinton’s home in Westchester, not her offices.