As the FBI warned there could be more suspicious packages moving through the mail — after pipe bombs addressed to former U.S. president Barack Obama, Hillary Clinton, CNN and other individuals were discovered — it confirmed late Wednesday that two suspicious packages addressed to Democratic Rep. Maxine Waters were also intercepted.

And a federal official told Reuters that investigators are also trying to track down a suspicious package they believe was addressed to former vice-president Joe Biden.

The Secret Service characterized the packages sent to Obama and Clinton as "potential explosive devices."

A law enforcement official told The Associated Press that the bombs were packed with powder and shards of glass.

There were no explosions and no reports of injuries, and the packages overall appeared to target prominent Democrats, as well as the news network most often criticized by hard-right conservatives.

The packages landed as often heated midterm election campaigns are occurring around the country. The Nov. 6 midterms have the potential to change the composition of the Senate and House of Representatives in the final two years of the term of President Donald Trump, who has often derided the Democrats and characterized CNN reporting as "fake news."

Speaking Wednesday afternoon, the president said, "Acts or threats of political violence have no place in the United States."

Watch as Trump talks about the federal investigation into the packages:

U.S. president addresses the incident where packages containing 'potential explosive devices' were sent to Hillary Clinton, Barack Obama and CNN 2:07

At a rally in Wisconsin on Wednesday night, Trump reiterated his earlier message and said an aggressive investigation is underway.

Speaking to a cheering crowd, Trump called for unity, saying, "We want all sides to come together in peace and harmony."

But he also said the media "has a responsibility to set a civil tone and to stop the endless hostility and constant negative and oftentimes false attacks and stories."

Trump's remarks calling for unity are likely to be greeted coolly by critics and many Democrats, as he has repeatedly called for the jailing of Hillary Clinton despite the fact the FBI concluded an investigation into her use of a private email server without recommending charges. Just in the past week at a rally, he praised a Republican congressman for bodyslamming a reporter last year.

Bubble wrap in manila envelopes

The FBI, which is investigating alongside the Joint Terrorism Task Force, said the suspicious packages it has identified as of Wednesday were sent to:

George Soros, a wealthy philanthropist and prominent Democratic donor.

Hillary Clinton, former Democratic presidential nominee and secretary of state.

Former president Barack Obama.

Former CIA director John Brennan, via CNN's New York office.

Former attorney general Eric Holder, who served under Obama. The package addressed to Holder didn't make it to his office, and was instead rerouted to a fake return address.

​The FBI said the packages were mailed in manila envelopes with a bubble wrap interior.

"The packages were affixed with computer-printed address labels and six Forever stamps," the FBI said. "All packages had a return address of DEBBIE WASSERMAN SHULTZ in Florida."

By late Wednesday, it appeared there could be two more cases.

The FBI says it's possible that more packages were mailed and is urging the public not to handle any suspicious packages. (FBI)

Maxine Waters said she had been told by police that her Washington office was also the target of a suspicious package. Waters, a long-serving member of the House of Representatives, has been a vocal critic of the president, who has in turn called her "an extremely low IQ person."

Possible suspicious package in L.A.

Later Wednesday, police in Los Angeles that they were investigating a suspicious package at a central mail facility.

"While we determine its contents and origins the facility is being evacuated," police said on Twitter.

"We are working closely with our federal law enforcement partners, given the number of suspicious devices discovered across the nation. As more information is available we will provide updates."

It wasn't immediately clear if the Waters package or the possible package in L.A. were connected to the other packages identified by the FBI. But a source told The Associated Press on Wednesday night that the package addressed to Waters and the one in L.A. appear similar to the New York and D.C. bombs.

The packages were intercepted or uncovered over several days. On Monday, an explosive device was found in a mailbox at the suburban New York home of Soros, the liberal billionaire who has been denounced by the president and vilified by right-wing conspiracy theorists. A Soros employee alerted authorities of the package, which they left in a wooded area near the home. A pipe bomb was later detonated, authorities said.

The Secret Service said the package addressed to Clinton was flagged as suspicious late Tuesday in Westchester county, N.Y. Clinton and her husband, former president Bill Clinton, have a residence in Chappaqua, N.Y.

A second package, addressed to the Washington, D.C., residence of Obama, was intercepted on Wednesday morning.

"The packages were immediately identified during routine mail screening procedures as potential explosive devices and were appropriately handled as such," the Secret Service said.

Powder deemed harmless: source

In New York City, the Time Warner building, home to CNN, was evacuated on Wednesday after the package was found.

The New York Police Department said a package in the mailroom of the Time Warner building, which also houses retail shops, contained what resembled a pipe bomb.

NYPD Commissioner James O'Neill said at a midday news conference the police bomb squad removed a device.

He said an envelope containing an unidentified white powder was also found. A law enforcement official later told The Associated Press that tests have determined that a powder found inside an envelope delivered to CNN along with a pipe bomb was harmless. The official wasn't authorized to discuss the investigation publicly and spoke on condition of anonymity.

Investigators have not offered details on a potential motive, but said that all the confirmed bombs appeared to come from the same person or persons.

No injuries reported

Neither Obama nor the Clintons were near the packages when they were flagged. Their mail screening does not occur at their residences, U.S. media outlets reported.

"Nothing made it to their home," Bill Clinton's spokesperson confirmed to Reuters in an email.

Hillary Clinton was not even in New York. She began a two-day stint in Florida on Tuesday, drumming up support for Democratic candidates contesting the midterm elections in two weeks.

Watch as Hillary Clinton talks about the packages, thanks the Secret Service.

Former U.S. secretary of state and Democratic presidential nominee Hillary Clinton addressed the news that a suspicious device was sent to her house. 0:51

At an event on Wednesday in Coral Gables, Fla., Clinton said she was grateful for the continued service and commitment of the Secret Service.

"It is a troubling time, isn't it? It's a time of deep divisions, and we have to do everything we can to bring our country together," she said. "We also have to elect candidates who will try and do the same."

Tension rising

In Manhattan, CNN president Jeff Zucker said the news organization was co-operating with the NYPD. Zucker added that CNN was checking its international bureaus.

In a statement released later Wednesday, Zucker took aim at the president and his staff.

U.S. Rep. Debbie Wasserman Schultz, Clinton, Soros and Obama are pictured in a combination photograph made from Reuters file photos. Federal authorities are investigating packages that were addressed from Wasserman Schultz and to the other three. (Gretchen Ertl/Kamil Krzaczynski/Luke MacGregor/Siphiwe Sibeko/Reuters)

"There is a total and complete lack of understanding at the White House about the seriousness of their continued attacks on the media," he wrote in a statement released by CNN. "The president, and especially the White House press secretary, should understand their words matter. Thus far, they have shown no comprehension of that."

Earlier in the day, the White House condemned the attempted attacks, saying in a statement that "these terrorizing acts are despicable and anyone responsible will be held accountable."

In a tweet, press secretary Sarah Sanders said the attempted attacks were "cowardly and unacceptable" and would not be tolerated. She also said that the administration's condemnation of the attempted attacks "certainly includes threats made to CNN as well as current or former public servants."

New York City Mayor Bill De Blasio urged all politicians and public figures to "turn down the temperature" on the rhetoric. "Don't encourage violence, don't encourage hatred, don't encourage attacks on media," he said.

See where some of the suspicious packages were sent.