Emergency service personnel with a bomb sniffing dog work outside the building that houses New York Governor Andrew Cuomo's office after a report of a suspicious package, Oct. 24, 2018, in New York.
Emergency service personnel with a bomb sniffing dog work outside the building that houses New York Governor Andrew Cuomo's office after a report of a suspicious package, Oct. 24, 2018, in New York.

WHITE HOUSE - Investigators are expressing confidence they will identify who is responsible for sending 10 pipe bombs to prominent Democrats and critics of U.S. President Donald Trump.

"We will identify and arrest the person or people responsible for these acts," New York City Police Commissioner James O'Neill told reporters Thursday afternoon.

All the "suspected explosive devices" were being taken to the Federal Bureau of Investigation's laboratory at the U.S. Marine Corps base in Quantico, Virginia, said O'Neill.

"We are discovering things by the hour," he added at a news conference where other officials also said tips from the public were providing leads for investigators.

FBI Assistant Director William Sweeney, who is in charge of the bureau's New York field office, said "the investigation is still in its early stages," so he would not provide specific answers to the media about possible suspects or whether the pipe bombs were properly wired to explode.

Explosive Devices
Police stand watch near a building associated with Robert De Niro after reports of a suspicious package, in New York, Oct. 25, 2018.

Investigators are specifically looking at the southern part of the state of Florida as a source of some of the packages, according to media reports.

Trump is largely blaming the media for the angry political atmosphere in America that critics contend has led to what is being regarded as a wide-scale assassination attempt.

"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," Trump said on Twitter on Thursday morning.

New packages meant for Biden, De Niro

Trump's tweet came as suspected explosive devices addressed to actor Robert De Niro and former Vice President Joe Biden were found Thursday.

Police in New York said one package was sent to a production company owned by De Niro and that it is similar to those sent to other prominent Democrats, including former president Barack Obama and former secretary of state Hillary Clinton. The New York City Police Department's bomb squad transported the suspected bomb in a special truck out of the Tribeca neighborhood Thursday.

The Federal Bureau of Investigation also confirmed two packages addressed to Biden were found in Delaware.

 

WATCH: Bomb Expert: Pipe Bomb Origins Are Easy to Detect

   

Other packages have been addressed to a former U.S. attorney general, two Democratic Party members of Congress and former Central Intelligence Director John Brennan.

Brennan, now a commentator for MSNBC network and NBC News, responded to Trump's tweet Thursday, tweeting "Stop blaming others. Look in the mirror. Your inflammatory rhetoric, insults, lies & encouragement of physical violence are disgraceful."

What police termed a live explosive device that arrived in an envelope addressed to Brennan at CNN's New York bureau prompted the evacuation of the Time Warner Center for hours Wednesday.

Pressed by reporters Thursday on whether there could be a link between Trump insulting political opponents and the dispatch of the bombs,  Sanders replied, "the president is certainly not responsible for sending suspicious packages to someone no more than [Democratic U.S. Senator] Bernie Sanders was responsible for a supporter of his shooting up a baseball field practice [by Republican lawmakers] last year."

President Donald Trump speaks at a rally at Centra
President Donald Trump speaks at a rally at Central Wisconsin Airport in Mosinee, Wis., Oct. 24, 2018.

Trump, lawmakers weigh in

Trump said at a rally late Wednesday that targeting government officials by sending them explosives "is an attack on our democracy itself."

Throughout the day Wednesday, leaders from both the major parties called for a return to civility in the political arena, a theme Trump picked up on at the rally.

"No one should carelessly compare political opponents to historical villains, which is done often and all the time. It's got to stop," said the president. "We should not mob people in public spaces or destroy public property. There is one way to settle our disagreements — it's called peacefully, at the ballot box. That's what we want."

House Minority Leader Nancy Pelosi and Senate Minority Leader Chuck Schumer, the top two Democrats in Congress, issued a statement Wednesday afternoon, accusing Trump of fanning the flames of political unrest.

"I think this is an act of political terrorism," Congressman Rodney Davis, a Republican from the state of Illinois, said on CNN early Thursday.?

Earlier targets 

The Secret Service says the package addressed to Clinton was discovered late Tuesday, intercepted at a mail screening facility near her home in a New York suburb where she lives with her husband, former President Bill Clinton.

A package containing a "live explosive device," ac
A package containing a "live explosive device," according to police, received at the Time Warner Center which houses the CNN New York bureau, in New York City, is shown in this handout picture provided by CNN Oct. 24, 2018.

A separate package addressed to Obama, according to the Secret Service, was intercepted at a screening facility at Joint Base Anacostia-Bolling, a 365-hectare military facility in Washington.

California Congresswoman Maxine Waters was sent two suspect packages, one intended for her office in the nation's capital and the other for her home district office. The first was intercepted at a congressional mail sorting center in the state of Maryland, and the second discovered by postal inspectors at the Los Angeles Central Mail Sorting Facility.

The gate is closed at the entrance to a house owne
The gate is closed at the entrance to a house owned by philanthropist George Soros in Katonah, N.Y., a suburb of New York City, Oct. 23, 2018.

The first in the series of explosive devices was found Monday in a mailbox outside the New York home of billionaire philanthropist George Soros, a major donor to Democratic candidates.

Ken Bredemeier and Masood Farivar contributed to this report.