Former Vice President Joe Biden and actor Robert De Niro -- both prominent critics of the Trump administration -- were the targets of suspicious packages discovered Thursday, officials said, one day after several similar parcels were sent to the homes and businesses of various Democratic politicos on Wednesday.

The FBI, New Castle County, Del., police and postal inspectors were investigating the package addressed to Biden, law enforcement officials told Fox News, stressing the suspicious package investigation was the bureau's highest priority. The FBI was also investigating a second package addressed to Biden at a postal facility in Wilmington. Both packages were similar to the others that were received. The FBI later confirmed the packages were addessed to Biden and De Niro

The FBI Laboratory at Quantico, Va., is also engaged, beginning forensic analysis of some of the packages addressed to former President Barack Obama, former Secretary of State Hillary Clinton, liberal billionaire George Soros, former Attorney General Eric Holder, former CIA Director John Brennan and California Democratic Rep. Maxine Waters.

Pictures of the contents of the Brennan package appeared to show a pipe bomb, but it wasn't clear if the explosive was in working order, and several experts took to social media to note flaws in the design. The Brennan device was also wrapped with a spoof flag of the terror group ISIS that bore the Larry the Cable Guy catchphrase "Get 'Er Done." It wasn't clear if either the Biden or De Niro packages contained similar contents.

The package addressed to "Joseph Robinette Biden Jr.," and bearing the return address of former Democratic National Committee head Rep. Debbie Wasserman Schultz, was discovered at a Delaware postal facility and did not reach Biden's house. Photos of the Biden packaging showed that the address stickers and postage stamps were nearly identical to the packaging found on the suspicious parcels from Wednesday. Biden no longer receives Secret Service protection, officials told Fox News.

Biden's house in Wilmington, was swept by authorities on Wednesday as a precautionary measure after the Obama, Clinton and Brennan packages were uncovered. That search did not turn up anything of note.

The suspicious package addressed to De Niro was discovered earlier Thursday in the mailroom of his production company, TriBeca Productions, a law enforcement source told Fox News. Security at the Tribeca Film Center called police because the package looked similar to the ones seen Wednesday, the law enforcement source said.

The NYPD Bomb Squad took an X-Ray and determined the package should be removed from the building and sent to a facility at Rodman’s Neck in the Bronx.

“A suspicious package was received. We called the police. They took it out and went through all safety procedures,” the Tribeca Film Center said in a statement. “It was addressed to Robert De Niro and is similar packaging to the others. It is an open investigation. Everyone is safe and the building is open.”

The FBI said Wednesday evening it had identified seven suspicious packages addressed to prominent Democratic figures over the last three days containing “potentially destructive devices.” The packages discovered Thursday would make it 10.

The bureau initially said it had recovered five packages that were similar in appearance and bore the return address of an office for Wasserman Schultz, D-Fla. The FBI said it was possible additional packages were mailed to other locations.

President Trump condemned the mailings on Wednesday and said a "major federal investigation is now underway."

"We have to unify. We have to come together," Trump said, at a bill-signing for opioid legislation. "Acts or threats of political violence of any kind have no place in the United States of America.”

On Thursday, he tweeted about the “anger” caused by the mainstream media.

“A very big part of the Anger we see today in our society is caused by the purposely false and inaccurate reporting of the Mainstream Media that I refer to as Fake News,” he wrote. “It has gotten so bad and hateful that it is beyond description. Mainstream Media must clean up its act, FAST!"

But even as Trump was placing the blame on the media, many of those targeted by the suspicious packages said Trump bore responsibility.

"Stop blaming others. Look in the mirror. Your inflammatory rhetoric, insults, lies, & encouragement of physical violence are disgraceful. Clean up your act...try to act Presidential. The American people deserve much better. BTW, your critics will not be intimidated into silence," Brennan tweeted.

Waters said in an interview with Blavity that the president "does a lot to promote violence."

De Niro, a longtime Trump critic, earlier this month said he felt “offended” by Trump and the GOP. He had previously said he would like to punch the president in the face.

Fox News’ Jake Gibson, Morgan Evans, Tamara Gitt, Brooke Singman contributed to this report