Updated at 11:59 a.m. ET
Federal investigators are searching for whomever sent a wave of suspicious packages addressed to political nemeses of President Trump.
Authorities discovered more packages Thursday morning addressed to former Vice President Joe Biden and the actor Robert De Niro, taking the total number of envelopes found to 10 and expanding the federal investigation into a slew of potential pipe bombs.
The FBI said two suspicious packages in Delaware were addressed to Biden, while the other was sent to De Niro in Manhattan.
The new items were "similar in appearance" to seven packages already discovered this week that had been sent to six other high profile critics of President Trump, including former President Barack Obama and former secretary of state Hillary Clinton, the FBI said.
The packages, which have contained potential explosive devices described by officials as potential pipe bombs, have sent jitters across the country and prompted calls from Republicans and Democrats for a cooling of political rhetoric.
The latest targets
Officials responded Thursday morning to a mail processing center in Delaware after one package addressed to Biden was recovered there.
In New York, meanwhile, police said a suspicious package was discovered in the Tribeca area of Manhattan in the early hours of Thursday morning. Officials confirmed the discovery to NPR, saying the matter is under investigation. That package contained a device similar to one recovered from the offices of CNN on Wednesday.
The package was found "at the business residence of Robert De Niro," New York Gov. Andrew Cuomo told NPR's David Greene. The Tribeca Grill, one of De Niro's restaurants, is at the corner of Greenwich and Franklin streets.
The New York Police Department says the package was reported around 4 a.m. in the area of Greenwich and Franklin streets in Tribeca. The police bomb squad responded, and it was "removed from the location," the NYPD says.
Suspicious packages also were sent to former President Barack Obama and former Secretary of State Hillary Clinton.
Others were addressed to former CIA Director John Brennan in care of CNN in New York, former Attorney General Eric Holder and Rep. Maxine Waters, D-Calif. The first package was reported on Monday at a residence of billionaire investor George Soros, who is an active supporter of Democratic causes.
The package addressed to Holder did not reach him at his lawfirm in Washington D.C.; instead it was rerouted to the return address affixed on the envelope — that of Florida Rep. Debbie Wasserman Schultz.
Wasserman Schultz's office was evacuated when the enveloped arrived on Wednesday. She said she was "deeply disturbed by the way my name was used."
Cuomo said the two suspicious devices found in New York City shouldn't stop people from going about their business as normal.
"Don't let the terrorists win," he said. "There's no reason to be afraid."
Attorney General Jeff Sessions said on Thursday that "across the administration, we condemn the actions that led to these activities in the strongest possible terms and are determined to make sure that we get to the bottom of it and justice is done."
Investigators are now working in New York and other cities, within the postal system, and at the federal level, to determine who sent the packages — and why.
The Secret Service has said suspicious packages were addressed to Clinton in Westchester County, N.Y., and to Obama's residence in Washington, D.C.; those packages contained explosive devices that were similar to one that was found on Monday at the home of George Soros — a frequent contributor to Democratic and progressive causes.
An explosive ordnance disposal team destroyed the package sent to Soros through a controlled detonation. Officials say investigators are analyzing the materials from that effort.
Trump was briefed at the White House on Wednesday on the investigation. He said the inquiry into the packages will have whatever resources are needed and FBI Director Christopher Wray has pledged that the bureau will not rest until the culprits are caught.
"This investigation is of the highest priority for the FBI," Wray said. "We have committed the full strength of the FBI's resources and, together with our partners on our Joint Terrorism Task Forces, we will continue to work to identify and arrest whoever is responsible for sending these packages."
But the FBI also has acknowledged that more suspicious packages may still be working their way through the mail and there is no way to know now how many there might ultimately be.