WASHINGTON — A series of "suspicious packages" containing potential explosives set off panic after the Secret Service reported intercepting one each addressed to Hillary Clinton and Barack Obama while CNN reported a third such device sent to its building in midtown Manhattan.

Packages containing potential explosives set off a wave of panic Wednesday after the Secret Service reported intercepting devices addressed to President Obama and Clinton, and others were discovered targeting former CIA chief John Brennan and former Attorney General Eric H. Holder Jr.

Law enforcement officials familiar with the investigation said authorities suspect at least two of the devices — possibly all — were made and sent by the same person or persons. The officials described an aggressive "full court press" to identify and capture the suspects.

"It appears that an individual or individuals sent out multiple similar packages," said John Miller, the NYPD's deputy commissioner of intelligence and counterterrorism.

Authorities have stepped up screening of other people across the country who could be targets, the official added.

On Monday, a similar explosive device was found at the suburban New York home of George Soros, the billionaire supporter of liberal causes. Soros' home in Katonah, N.Y., is a short drive from the home that President Bill Clinton and Hillary Clinton own in Chappaqua.

Like the others, Soros has been a frequent target of conservative political figures and media.

A law enforcement official familiar with the investigation said the devices sent to Clinton and Obama were "similar in design" to the one sent to Soros. The official, speaking anonymously because they were not authorized to discuss it publicly, said security services suspect there may be other devices.

A sixth package, addressed to California Democratic Rep. Maxine Waters, was also being scrutinized, a law enforcement official said.

The motive was not immediately clear. The list of liberal targets suggested a political intent, but the sender may also be trying to create that impression or be motivated by personal grudge or other unknown reasons.

Obama, Clinton, Brennan and Holder have been the subject of frequent attacks by President Donald Trump and other conservatives. Trump has criticized Obama's foreign policy and economic policies, and he has led chants at political rallies of "lock her up" about Clinton, the former first lady and secretary of state whom Trump defeated in the 2016 presidential race.

Trump revoked Brennan's security clearance in August, in what many considered an act of retaliation over his frequent public criticisms of Trump. As Obama's attorney general, Holder long aggravated conservatives and later was hired by the California state legislature to represent its interests against the Trump administration.

The package to Brennan was sent via CNN's New York office. CNN anchors, speaking live from cellphones outside their bureau at the Time Warner Center, described the evacuation of a New York landmark that disrupted traffic and drew the New York Police Department's bomb squad.

Brennan does not work for CNN, but he is a contributor to NBC and MSNBC. A police source in New York confirmed that a package was sent to the building.

The package to Holder apparently ended up at the offices of Florida Rep. Debbie Wasserman Schultz, a Democrat.

Law enforcement officials said several of the packages had Wasserman Schultz's name as the return address. When the package to Holder could not be delivered, it was sent to her Florida office, a law enforcement official said.

Most of the packages were sent in manila envelopes, typed in all capital letters and with multiple stamps, they added. One law enforcement official described the devices as pipe bombs made of lightweight material, though it was unclear whether they were capable of exploding.

NYPD Commissioner James O'Neill said the Brennan package sent to the CNN mailroom "appeared to be a live explosive device" and that an unknown white substance was found. CNN tweeted a picture of the package, showing Wasserman Schultz's name on the return address and Brennan as the addressee. Both of the names, as well as the word "Florida," were misspelled.

Wasserman Schultz was chairwoman of the Democratic National Committee until she was forced to resign in 2016 over complaints that she was favoring Clinton over her Democratic primary rival, Sen. Bernie Sanders, I-Vt.

On Wednesday, Hillary Clinton addressed the situation during a campaign appearance in Florida, expressing her gratitude to the Secret Service for intercepting the package and her fear about a difficult and dangerous moment for the country.

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

New York Gov. Andrew Cuomo, speaking at a news conference with law enforcement officials and New York Mayor Bill de Blasio, said his office had also received a suspicious package. But that turned out to be a false alarm, as did reports of a package sent to a San Diego building.

The New York officials said law enforcement planned to increase its visibility at other potential targets, including media offices, but said they had no more specific, credible threats in New York.

"This is a political year. It's a political season. We are weeks from an election and that's obviously in the air and that's an obvious factor," Cuomo said.

Both elected leaders referred to the series of mailed pipe bombs as attempted terrorism. "What we saw here today was an effort to terrorize," De Blasio said.

The White House sent a statement after initial reports naming Clinton and Obama.

"We condemn the attempted violent attacks recently made against President Obama, President Clinton, Secretary Clinton and other public figures," press secretary Sarah Huckabee Sanders said. "These terrorizing acts are despicable, and anyone responsible will be held accountable to the fullest extent of the law. The United States Secret Service and other law enforcement agencies are investigating and will take all appropriate actions to protect anyone threatened by these cowards."

Trump made no immediate comment but retweeted Vice President Mike Pence's condemnation while adding that he agreed "wholeheartedly!" with Pence's tweet that "these cowardly actions are despicable & have no place in this country."

The Secret Service said the packages addressed to Obama in Washington and Clinton in Westchester County, N.Y., were identified late Tuesday and early Wednesday, respectively, by Secret Service personnel "during routine mail screening procedures as potential explosive devices and were appropriately handled as such."

"Both packages were intercepted prior to being delivered to their intended location," according to the statement from Mason Brayman, assistant special agent in charge with the United States Secret Service. "The protectees did not receive the packages nor were they at risk of receiving them."

"The Secret Service has initiated a full scope criminal investigation that will leverage all available federal, state, and local resources to determine the source of the packages and identify those responsible," Brayman said.