A package was intercepted at a NY post centre, reportedly addressed to James Clapper. Another was discovered at a Manhattan postal facility and was addressed to former national intelligence director James Clapper at CNN's address. Investigators were likely relying on that system to pinpoint where some of the packages were mailed.
De Niro released a statement Friday calling on Americans to vote.
Authorities from across the U.S, government, including the director of Homeland Security, have either tied the bombs to south Florida or said they "originated" here.
The FBI says a suspicious package addressed to New Jersey Democratic Senator Cory Booker has been recovered in Florida and is similar in appearance to the other ones received in the last few days.
"There's a rich treasure trove of forensic information since they were found intact", Doherty said.
A law enforcement official familiar with the investigation said a suspicious powder from one package was tested and initially deemed not to be anthrax or a known agent.
Two law enforcement officials say a person was taken into custody in Florida in connection with package bombs that were sent to high-profile critics of the president. Bomb experts and security analysts say based on their rudimentary construction it appeared they were probably created to sow fear than kill.
George Soros, a billionaire philanthropist who has backed Democrats, also uses a courier that picks up his mail at a post office, goes through and delivers the filtered items to his home, the source said.
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.
"I am confident that this person or people will be brought to justice".
The common thread among the bomb targets was obvious: their critical words for Trump and his frequent, harsher criticism in return.
Former vice president Joe Biden was among those targeted with the glass-filled devices on Thursday.
President Donald Trump continued to turn attention to the media in the aftermath of the spate of suspected mail bombs sent to CNN and some of his prominent critics, this time complaining that the cable news network was casting blame on him.
None of the packages have detonated and no one has been hurt.
One federal law enforcement source told Reuters that authorities were investigating whether other individuals were involved and did not rule out further arrests. Wray said the bombs sent in the case were "not hoax devices". Bomb experts and security analysts say that based on their rudimentary construction it appeared they were more likely created to sow fear rather than to kill. Sweeney said the powder contained in envelopes holding the devices found in NY did not pose any biological threat and said the substance was still being analyzed. Each had computer-printed address labels and six stamps, the agency said.
His remarks came after he has blamed the media this week for rising "anger" in the country while refusing to acknowledge his own role in contributing to divisive rhetoric in the public discourse.
Clapper, who has frequently criticized Trump, vowed to CNN Friday morning that he wouldn't be intimidated in light of the discovery.