Authorities recovered new explosive devices Thursday morning that were mailed to former Vice President Joe Biden and award-winning actor Robert De Niro as the total number of bombs recovered by authorities grew to 10 and investigators further ramped up efforts around the country to find out who is behind the threat.

A senior law-enforcement official said that the device sent to De Niro was “identical” to the crudely made devices—described as pipe bombs—that were mailed via the United States Postal Service to former President Barack Obama in Washington, D.C., former Secretary of State Hillary Clinton at her home outside New York City, and to CNN headquarters in Manhattan.

While police in New York were investigating the device sent to De Niro, authorities in Delaware recovered two packages addressed to Biden that are similar to those that have surfaced across the country, according to the FBI.

The FBI on its Twitter account confirmed that the three new packages are “similar in appearance to the others.” All the packages are being sent to the main FBI laboratory in Quantico, Virginia for extensive tests to determine how the bombs were built and recover any evidence that might help lead investigators to a suspect or suspects.

The ten suspicious packages recovered by authorities as of Thursday morning include two addressed to Rep. Maxine Waters (D-CA) and one each to former Attorney General Eric Holder and billionaire philanthropist George Soros.

So far, packages with bombs have surfaced in New York, Delaware, Maryland, Los Angeles, and Florida, the FBI said, with authorities not ruling out the possibility of more.

None of the bombs have detonated or reached their intended target, and no one has been injured, but law enforcement say that nearly all of the devices were capable of causing significant harm. Authorities have not released any details about a suspect and said they expect more such packages to surface as the unease and law enforcement investigation enters its fourth day.

Police around the country have been visiting media outlets and prominent officials and stepping up their presence at strategic locations. To provide a sense of the fever pitch, the NYPD said it has seen a 139 percent increase in calls to its tip line.

Still there was little outward sign that authorities were closing in on a culprit or culprits.

During a 25-minute briefing in New York, authorities kept details close to vest , saying they did not want to give away details that would hurt the investigation or hinder prosecution.

William Sweeney, the head of the FBI’s New York field office, said that joint terrorism taskforce offices around the country are “fully engaged on this investigation,” adding that authorities are working quickly to process information from the packages recovered.

In New York, Sweeney noted, the agencies working on the case include the FBI, NYPD, U.S. Postal Service, ATF, and U.S. Secret Service, along with New York State Police and other local, state, and federal agencies.

The white powder contained in a package sent to CNN was determined not to be a biological agent but other tests were being conducted, Sweeney said, declining to go into further detail about exactly what it was.

“We are investigating all of this with great precision. I can tell you with great certainty that we will identify and arrest a person or people responsible for these acts,” said NYPD Commissioner James O’Neill.

"It’s absolutely terrorism ," said New York City Mayor Bill de Blasio, "because it’s an effort to use violence to make a political impact, and that’s the definition of terrorism."

All of the bombs were recovered intact except the one delivered to Soros' home, which was disrupted because it was considered “energetic,” meaning it was releasing level of energy that investigators believed posed a danger, a senior law enforcement official said.

As of Wednesday afternoon, all the bombs recovered so far had been transferred to the FBI lab where they were undergoing extensive tests.

Authorities would not elaborate about the functionality of the bombs, only saying that they are “treated as live devices,” as O’Neill put it.

One senior law-enforcement official said part of the reason for the vagueness right now is that “psychologically we’re not trying to coax or dare this person [or persons] to step up their game.”

The packages began surfacing Monday night when one was discovered in the mailbox at Soros’ Westchester County home and then increased in frequency on Wednesday when authorities recovered pipe bombs addressed to Clinton, Obama, Waters, and Holder—all major players in Democratic Party politics.

The first package Thursday was reported in lower Manhattan, where the NYPD responded to a call around 5 a.m. at 375 Greenwich St., offices that are home to DeNiro’s Tribeca Productions and Tribeca Grill, the restaurant the actor c0-owns, the NYPD said.

A retired NYPD intelligence detective who now works on the security team for the production company called the NYPD regarding a suspicious package that was similar to one in a photo released by the NYPD from CNN headquarters, the official said. That device, which officials told The Daily Beast was a crude but functional bomb, was addressed to former CIA director John Brennan and mailed to the CNN offices at the Time Warner Center on the edge of Central Park. Brennan is contributor to NBC and MSNBC.

One senior law-enforcement official said the package sent to De Niro “appears to be from the same sender” and contains “similar contents as previous packages.” A second official said “it’s identical to yesterday,” referring to packages received by others.

De Niro has been repeatedly critical of President Trump, saying at the Tony Awards ceremony in June: “I’m going to say one thing, fuck Trump. It’s no longer ‘Down with Trump.’ It’s fuck Trump.”

A woman who says she works in nearby 388 Greenwich Street—the global headquarters of Citigroup—posted a video showing fire trucks nearby on Thursday morning.

The NYPD bomb squad responded and examined the package using an X-ray tool and determined a crude pipe bomb was inside the package. About 90 minutes after police arrived, the package was contained and taken to a police range at Rodman’s Neck on an NYPD bomb truck with a full police escort before being transported to the FBI lab.

A preliminary investigation determined that the package was likely delivered to the mailroom of De Niro’s building earlier in the week, one senior law-enforcement official said.

The retired detective alerted police after seeing reports of the package delivered to CNN and realizing it was similar to one he had seen at the production studio, police said.

The package had a return address for an office used by Democratic Rep. Debbie Wasserman Schultz in Florida, similar to the address found on the other packages, the official said. Like the other bombs, it was wrapped in bubble wrap in a manila envelope and with the congresswoman's last name misspelled and eight American flag postage stamps.

Around 8 a.m., a package addressed to Biden was recovered from a U.S. mail facility in New Castle, Delaware, according to the FBI.

A short while later, a second package addressed to Biden was intercepted at a mail facility in Wilmington, Delaware.