Several US media reported that the suspect was taken into custody for questioning in Florida.
The US government on Friday announced a suspect had been arrested in connection with 12 suspicious packages and pipe bombs sent to critics of Donald Trump in a days-long spree that has inflamed the United States ahead of key midterm elections.
A Department of Justice spokeswoman announced the arrest on Friday morning, saying a news conference would be held at 2:30 pm (1830 GMT).
US media said the suspect was taken into custody in Florida, where a huge nationwide manhunt mobilizing hundreds of agents, had reportedly concentrated in recent hours.
Since Monday homemade bombs and other suspected explosive devices have been addressed to Barack Obama, Hillary Clinton, Hollywood megastar Robert De Niro and a litany of figures loathed by the US president's supporters.
Early Friday, an 11th package to Cory Booker, a New Jersey senator often touted as a Democratic presidential hope, was intercepted in Florida, the FBI confirmed.
A 12th package, identified by police as a pipe bomb similar to others found across the country, was found at a US Post Office in Manhattan and the bomb squad were dispatched, New York police said.
James Clapper, among a string of former intelligence chiefs critical of Trump, was the addressee of the 12th package, sent care of CNN.
On Wednesday, the news network evacuated its New York bureau after a similar package was found in the mail room addressed to another frequent CNN guest, former CIA director John Brennan.
Politicians on both sides of the aisle have branded the packages — intercepted in New York, Maryland, Florida, Delaware and Los Angeles — domestic terrorism, but Trump has come under fire for his response.
"Republicans are doing so well in early voting, and at the polls, and now this 'Bomb' stuff happens and the momentum greatly slows – news not talking politics," Trump tweeted Friday in remarks bound to enrage his opponents.
Trump Under Fire
"Very unfortunate, what is going on. Republicans, go out and vote!"
New York's state Democratic Governor Andrew Cuomo was unimpressed.
"Leaders have to be more responsible and the American public have to demand that responsibility," he told CNN.
Even before his Friday tweet bemoaning slacking Republican momentum, Trump came under criticism from the left for tempering calls for unity in the wake of the attacks, by lashing out at the press for stirring up "anger."
The White House has been forced to defend the president over accusations that he was not taking the attempted bombings seriously enough.
Trump recently endorsed the body-slamming of a reporter, routinely denounces the press as "fake news" and has leveled toxic remarks in the past against the pipe bomb targets.
Cuomo insisted that the investigation was making "significant progress" despite the dearth of leads announced publicly and no known arrests.
US media has reported that much of the investigation has focused on Florida, where officials believe that at least some of the packages were dispatched.
De Niro Urges Voting
"The focus on Florida is going to bear through," Cuomo told CNN. "My instinct is they are going to have results there on the specifics of the manhunt."
Cuomo disputed speculation that the devices were not rigged to explode.
"No one can say there were fake bombs, they were dangerous," he said. "There may be questions about the levels of sophistication."
The packages were sent in manila envelopes with bubble wrap, marked with computer-printed address labels. Each listed Debbie Wasserman Schultz, former chairwoman of the Democratic National Committee, as the sender, including misspellings of her last name, the FBI said.
Double Oscar winner and biting Trump critic De Niro on Friday urged people to vote in the November 6 elections, one day after a device was discovered at the Manhattan offices of his production company.
"I thank God no one's been hurt, and I thank the brave and resourceful security and law enforcement people for protecting us," he said. "There's something more powerful than bombs, and that's your vote. People MUST vote!"
"This is definitely domestic terrorism," Clapper told CNN Friday, hitting out at Trump saying he bore "some responsibility" for a decline in civility.
"I'm not suggesting a direct cause and effect relationship between anything he's said or done and these — and the distribution of these explosives," Clapper told CNN.
"But I do think he bears some responsibility for the coarseness of civility in this country. He needs to remember that his words count."