A 56-year-old man has been arrested in Florida in connection with a mail-bombing campaign aimed at critics of US President Donald Trump.
US officials named the man as Cesar Sayoc. He faces five charges including mailing explosives and threatening ex-presidents.
Mr Trump said the acts were “despicable and have no place in our country”.
Fourteen items have been sent in recent days to figures including ex-President Barack Obama and actor Robert de Niro.
Two were found in Florida and New York City on Friday morning.
Later, two more were discovered in California. Billionaire and Democrat donor Tom Steyer said that a package sent to him had been intercepted at a mail facility in Burlingame, and another addressed to Democrat Senator Kamala Harris was reported in Sacramento.
How did Mr Trump react?
The president praised law enforcement for the quick arrest of the suspect, describing the search as looking for a “needle in a haystack”.
“These terrorising acts are despicable and have no place in our country,” he said.
The comments were in stark contrast to Mr Trump’s tweet earlier in the day, when he suggested the incidents, which he described as “‘Bomb’ stuff”, were slowing Republican “momentum” in early voting.
“I heard he was a person that preferred me over others. There’s no blame, there’s no anything,” Mr Trump said.
Former intelligence chief James Clapper, one of the recipients of Friday’s packages, told CNN: “This is definitely domestic terrorism, no question in my mind.”
He said that anyone who had been a critic of President Trump needed to be on the alert and take extra precautions.
“I’m not suggesting a direct cause-and-effect relationship between anything he’s said or done and the distribution of these explosives. But I do think he bears some responsibility for the coarseness of civility of the dialogue in this country,” he added.
How Cesar Sayoc was caught?
He was at a vehicle parts shop in the city of Plantation, Florida.
FBI Director Christopher Wray revealed that he was detained after his fingerprint was allegedly found on one of the packages.
“Let this be a lesson to anyone, regardless of their political beliefs, that we will use the full force of the law against you.”
What do we know about Cesar Sayoc?
Law enforcement agencies said Mr Sayoc lives in Aventura, Florida.
Following his arrest, US TV broadcast live images of a white van, said to belong to Mr Sayoc, being loaded on to a trailer in Plantation and towed away for examination.
The van’s windows were covered in images. One piece of artwork depicted President Trump standing on a tank and another showed Hillary Clinton with a bullseye superimposed on her face.
Twitter and Facebook accounts in the name of Cesar Altieri and Cesar Altieri Randazzo respectively, believed to be used by the suspect, have been taken down.
How did the bomb threat unfold?
The series of bomb alerts began on Monday, when a suspected device was found in the post box of billionaire businessman George Soros, a major Democratic Party donor.