The CNN bureau in New York received a device looking like a pipe bomb, leading police to evacuate the building, and New York Governor Andrew Cuomo, a Democrat, said his office also received a suspicious package.
X-ray images show that the package addressed to De Niro contains a device similar to the pipe bombs found in other packages this week that were addressed to prominent critics of Trump, the two sources said.
The package with Biden's name on it was found at the facility in New Castle, Delaware on Thursday morning.
At least eight parcels were intercepted before reaching any intended recipients, including Obama's attorney-general, Eric Holder, former Central Intelligence Agency director John Brennan and prominent Democratic Party donor George Soros.
According to the NYPD's chief of counterterrorism, the explosive appeared to be sent by the same person who mailed suspicious packages to the Clinton and Obama homes, as well as the device found on Monday at the home of billionaire philanthropist George Soros.More news: Saudi assistance will help Pakistan reduce International Monetary Fund burden: PM Imran
A member of the Broward County Sheriff's Office bomb squad walks to the building where U.S. Rep.
Authorities said on Wednesday the pipe bombs were packed with shards of glass and were intercepted.
The targets of the bombs were some of the figures most frequently criticized by Trump, who still assails Clinton at rallies while supporters chant "lock her up" - two years after he defeated her and she largely left the political scene.
Very early Thursday morning, President Trump appeared to indirectly address speculation that his own incendiary rhetoric against the media may have inspired said perpetrator.
The CNN bureau in NY received a package addressed to Brennan, who has appeared as a CNN analyst, leading police to evacuate the Time Warner building in a busy Manhattan neighborhood near Central Park. "It has gotten so bad and hateful that is beyond description".
The package addressed to De Niro came around the same time officials intercepted a similar one addressed to former vice president Joe Biden.
There has been no claim of responsibility.More news: 'We've paid a big price': Australia government loses crucial by-election
CNN's NY bureau in midtown Manhattan was also reportedly sent a package.
The New York Police Department says the package was reported around 4 a.m. ET, in the area of Greenwich and Franklin streets in Tribeca.
On Wednesday, authorities were at Biden's home in Greenville, Delaware after a suspicious package addressed to him was intercepted in Washington, D.C., say sources.
FBI investigators are working around the clock to identify the source of the suspicious packages, and say it is extremely helpful that none of the devices detonated, which will help them trace the source.
"Mainstream Media must clean up its act, FAST!" he continued.
"Acts or threats of political violence have no place in the United States", Trump said.More news: Turkey to reveal details of probe into Khashoggi’s killing on Tuesday