Video report by ITV News Reporter Mark McQuillan
A man has been charged in connection with the mail-bombing incidents targeting prominent critics of President Donald Trump.
Cesar Sayoc, aged 56, was identified after a fingerprint was found on one of the suspect packages, the FBI said.
Sayoc, from Florida, is accused of sending more than a dozen pipe bombs through the mail to prominent Democrats including former President Barack Obama and Hillary and Bill Clinton, as well as the offices of CNN.
He has been charged with five federal offences, including the illegal mailing of explosives. The charges carry a maximum of 58 years in prison.
Attorney General Jeff Sessions said the case showed that regardless of anyone's political beliefs, "the full force of the law" would be brought against anyone making such threats.
Mr Sessions said that more than a dozen suspicious packages had been sent through the US postal service to various targets.
"This is utterly unacceptable," he said. "Political violence or the threat of violence is antithetical to our vigorous system of self government."
He added: "Let this be a lesson to anyone, regardless of their political beliefs, that we will bring the full force of law against anyone who attempts to use threats, intimidation and outright violence to further an agenda. We will find you, we will prosecute you to the fullest extent of the law."
FBI Director Christopher Wray said that the 13 devices intercepted were not hoax devices.
He said a fingerprint from one of the envelopes containing a device addressed to Congresswoman Maxine Waters matched that of Sayoc.
There was also a possible DNA connection between two of the suspicious packages and a sample previously taken from Sayoc, he said.
"Today's arrest doesn't mean we are all out of the woods," Mr Wray said. "There may be other packages in transit now and other packages on the way so we need the help of everyone out there to help with this investigation in the days to come."
Mr Sayoc was arrested in a car park of an AutoZone auto parts store in Plantation, Florida, west of Fort Lauderdale.
Shortly afterwards, law enforcement officials were seen seizing a van parked in the car park thought to be connected to the suspect. The van was covered in a range of stickers including images of President Trump and American flags.
The arrest comes after more suspicious packages addressed to US senator Cory Booker and former director of national intelligence James Clapper - similar to others sent to high profile figures in the US - were intercepted on Friday.
A series of 13 devices have been sent to prominent Democratic and media figures over the past week - all of whom are critics of president Donald Trump.
The package addressed to senator Booker was intercepted in Florida, while the one addressed to Mr Clapper was intercepted in New York City.
Speaking shortly after Sayoc's arrest, President Trump commended the "incredible job" carried out by law enforcement officials promised that the perpetrator will be prosecuted to "fullest extent of the law".
He said: "These terrorising acts are despicable and have no place in our country.
"We must never allow political violence to take root in America and I am committed to do anything in my power as president to stop it and to stop it now.
"The bottom line is that America must unify and we must show the world that we are united together in peace and love and harmony as fellow American citizens.
"There is no country like our country and every day we are showing the world just how truly great we are."
John Miller, NYPD Commissioner of Intelligence and Counterterrorism told reporters a pipe bomb "consistent with other devices we've seen this week" had been found and recovered Friday from a postal facility in New York.
According to Miller, the device came inside a package that a postal worker immediately recognised before alerting police on scene.
He said the package was screened and isolated before it was placed inside a bomb truck and transported safely on the highway, he added.
Former presidents Barack Obama and Bill Clinton and former vice president Joe Biden were also sent packages, along with a host of other prominent figures including Hillary Clinton and actor Robert De Niro.
Authorities have warned there may be more.
The mail bomb campaign came less than two weeks ahead of US congressional elections that could alter the balance of power in Washington.
Mr Biden called for an end to the "hatred" and "ugliness" in US politics and said he hoped one positive that may come out of the attacks is that people will realise "we have to begin to put this country back together again".
Congresswoman Debbie Wasserman Schultz of the US state of Florida who was also targetted, said that she and other critics of Trump would "never be cowed into submission".
Speaking at the university of Buffalo on Thursday night, Biden made the pointed remark that "words matter".
Former vice president Biden said: "My hope is this recent spate of these, who knows exactly what they were, but these pipe bombs being mailed, might wake everybody in my business up a bit. And realise that we have to begin to put this country back together again. This division, this hatred, this ugliness, it has to end."
Earlier, Mr Trump doubled down on his criticism of CNN - one of the targets of the bombs.
In a pre-dawn tweet the president said "lowly rated CNN" criticises him at will, "even blaming me for the current spate of Bombs".
Who has been targeted so far:
Bill and Hillary Clinton
CNN office (New York), addressed to former CIA Director John Brennan
Debbie Wasserman Schultz (Democrat congresswoman)
Andrew Cuomo (New York governor)
Maxine Waters (Democrat congresswoman)
Attorney General Eric Holder
Robert De Niro
Cory Booker (Democrat senator)
James Clapper (former Director of National Intelligence)