The man suspected of being behind a plot in which more than a dozen mail bombs were sent to prominent critics of US President Donald Trump has been charged with five federal crimes.
Florida resident Cesar Sayoc, 56, is accused of inter-state transportation of an explosive, mailing of explosives, threats against former presidents and threatening inter-state communications, said FBI chief Christopher Wray.
If put on trial and convicted, he faces up to 48 years in prison.
Mr Sayoc, a registered Republican with a lengthy criminal history, was taken into custody in the Miami area of Florida, a US law enforcement official said.
Law enforcement agencies are still investigating whether other people may have been involved in sending the packages.
Local television news stations showed investigators covering a white van with a blue tarp at an AutoZone car park in Plantation, near Fort Lauderdale.
Public records show that Mr Sayoc has been arrested numerous times over the years, including one case in which he was accused of threatening to use a bomb.
His white van, which was seized by authorities, had numerous stickers showing US President Donald Trump and Vice-President Mike Pence, as well as a "CNN SUCKS" sign.
Mr Sayoc is a promoter, booking agent and "live entertainment owner," according to his LinkedIn profile, which listed him as the owner of International Gold Productions.
He filed for bankruptcy in Miami in 2012, according to court records. At the time, he said he lived with his mother in Aventura, Florida, and listed a $1,150 tax refund and a 2001 Chevy Tahoe vehicle as his only assets.
No one had claimed responsibility for parcel bombs, which were denounced by authorities as terrorism, and came less than two weeks ahead of US congressional elections that could alter the balance of power in Washington.
FBI Director Christopher Wray said at least 13 mail bombs had been intercepted but warned that further suspicious packages may have been sent.
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President Trump hailed the "incredible job" by law enforcement officers during the week. He said "we must show the world that we are united".
But he said that the bomb scares were slowing Republican "momentum" ahead of the midterm elections in November.
"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," he tweeted.
"Very unfortunate, what is going on. Republicans, go out and vote!"
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A federal law enforcement official said earlier today that the focus had intensified on Florida as a key location for the investigation and possible point of origin of the packages.
Police closed roads around the AutoZone car park and helicopters flew overhead.
All the people targeted by the suspicious packages have often been maligned by right-wing critics.
They included Democratic Party donor George Soros, former President Barack Obama, former Vice President Joe Biden, and former Secretary of State and presidential candidate Hillary Clinton.
The FBI has said that at least five of the packages bore a return address from the Florida office of US representative Debbie Wasserman Schultz, a former chair of the Democratic National Committee.
More packages discovered today
Earlier today, authorities found two more suspicious packages addressed to US Senator Cory Booker and James Clapper, the former US director of national intelligence.
The discoveries came amid a manhunt for the person who sent bombs to prominent Democrats and critics of Mr Trump.
A 12th package was addressed to Mr Clapper, the former director of national intelligence, and sent to CNN, the cable network reported.
"This is definitely domestic terrorism, no question about it in my mind," Mr Clapper said on CNN.
Another package was sent to US Senator Kamala Harris, a California Democrat who has criticised Mr Trump.
Meanwhile, a local police bomb squad and canine units joined federal investigators yesterday to examine a sprawling US mail distribution centre at Opa-Locka, northwest of Miami, Miami-Dade County police said.
US Homeland Security Secretary Kirstjen Nielsen said Florida appeared to be the starting point for at least some of the bomb shipments.
Authorities believe the packages, which were intercepted before reaching their intended recipients, all went through the US Postal Service at some point, a source said.
None detonated and no one has been hurt.
The devices were thought to have been fashioned from bomb-making designs widely available on the internet, a federal law enforcement source told Reuters.
Still, investigators are treating the devices as "live" explosives, not a hoax, said James O'Neill, the New York City police commissioner. Two of the parcels surfaced there.
"It does remain possible that further packages have been or could be mailed," William Sweeney, assistant director of the FBI, told a news conference in New York.
