Federal authorities made an arrest on Friday in connection with the nationwide bombing campaign against outspoken critics of President Trump, a significant breakthrough in a case that has gripped the country in the days leading up to the midterm elections.
A law enforcement official identified the suspect as Cesar Sayoc, 56, of Aventura, Fla. The official said Mr. Sayoc had a criminal history and ties to the New York area.
Also Friday morning, Florida news organizations reported that the authorities had surrounded a white van with Trump stickers on it.
The arrest came only hours after the mysterious spate of pipe bombs spread further as federal authorities said on Friday morning that they had found two more of the explosive devices: one addressed to Senator Cory Booker and the other to James R. Clapper Jr., the former director of national intelligence.
Although no formal charges have been filed yet, two of the law enforcement officials said there was a high likelihood that Mr. Sayoc would be prosecuted at least in part in Federal District Court in Manhattan. The F.B.I.’s New York office has been leading the investigation and five of the bombs sent this week fall under the jurisdiction of the United States attorney’s office in Manhattan.
The package addressed to Mr. Clapper was meant to be delivered to the New York offices of CNN, where he works as an analyst, but was intercepted at a mail facility in Midtown Manhattan, police officials in New York City said. The package addressed to Mr. Booker, a New Jersey Democrat, was found in Florida, which two people briefed on the matter have said has become a focus of the intense, nationwide investigation into the bombs.
At a news conference on Friday morning, John Miller, the New York Police Department’s deputy commissioner of intelligence and counterterrorism, said a postal worker at the mail facility on 52nd Street recognized the package addressed to Mr. Clapper as similar to other suspicious packages discovered this week and “froze it in the system.”
The department’s bomb squad responded to the facility and secured the package for delivery to an F.B.I. lab in Quantico, Va., Mr. Miller said.
Speaking on CNN on Friday, Mr. Clapper said he was not surprised that a device had been sent to him. He has been a frequent critic of President Trump, a similarity shared with everyone whose names have appeared on the packages discovered so far.
“This is definitely domestic terrorism,” Mr. Clapper said. “Anyone who has in any way been a critic, publicly been a critic of President Trump, needs to be on an extra alert.”
Mr. Clapper also said that on Wednesday night he had taken precautions after the first packages were discovered. While he and his wife were away from their home this week, he added, he told his neighbor not to collect their mail.
All together, 12 crude explosive devices have been found since Monday, sent through the mail to a host of Democrats and other prominent figures who have been among Mr. Trump’s most vocal detractors. The packages — virtually identical in plain manila envelopes — have been addressed to former President Barack Obama; former Vice President Joseph R. Biden Jr.; former Secretary of State Hillary Clinton; Representative Maxine Waters of California; former Attorney General Eric Holder; John O. Brennan, a former C.I.A. director, the actor Robert De Niro; and George Soros, the billionaire Democratic donor.
All of the envelopes had return address labels bearing the misspelled name of Representative Debbie Wasserman Schultz, a Democrat whose district is in southern Florida. None of the devices inside have exploded on their own so far, and investigators are still seeking to determine whether they were even capable of detonating. But the authorities in New York and elsewhere have warned that the devices should be considered dangerous.
The first package was discovered on Monday afternoon at the suburban New York home of Mr. Soros. While investigators initially thought that some devices were hand delivered, they now believe it is likely all of them were sent in the mail. Using information collected by the United States Postal Service, investigators have focused their attention on certain Florida postal centers, including one in Opa-locka near Miami.