Two additional pipe bombs, one addressed to former Vice President Joseph R. Biden Jr. and the other to actor Robert De Niro have been found, law enforcement officials said on Thursday, the latest in a wave of similar devices sent to several prominent Democrats who have been have been the rhetorical targets of President Trump and several right-wing figures.
A law enforcement official said the envelope and printed address labels on the package sent to Mr. De Niro were similar to those on explosives sent to former President Barack Obama, former Secretary of State Hillary Clinton and others, and an X-ray showed it contained a similar device resembling a pipe bomb.
“This appears to be from the same sender,” the official said.
The United States Postal Service records images of mail that comes into its system. Officials searched those images overnight and found several other suspicious packages, a law enforcement official said. It was not immediately clear how many they discovered.
Mayor Bill de Blasio of New York said Thursday that an “eagle-eyed security employee” at TriBeCa Productions noticed similarities between the package and photos of envelopes that were discovered on Wednesday.
They have featured half-a-dozen first-class postage stamps on manila envelopes lined with Bubble Wrap and bearing return addresses with the name of Debbie Wasserman Schultz, the Florida congresswoman who was once chairwoman of the Democratic National Committee. The mailing labels were computer-printed.
Some packages, including the device delivered to CNN’s offices in New York, arrived by courier, a law enforcement official said. Mr. de Blasio said that the authorities did not know whether that meant the sender of the devices lived in the New York area.
“We certainly don’t know whether they are here or elsewhere in the country” Mr. de Blasio said on CNN on Thursday morning. “There is somebody by definition who is a serial bomber, yes, and a terrorist.”
The mayor said he did not know yet whether the package addressed to Mr. De Niro in Lower Manhattan on Thursday was hand-delivered by a courier or whether it arrived through the mail. In anticipation of additional packages being found on Thursday, the Police Department has deployed additional officers outside news media offices and elected official’s offices, Mr. de Blasio said.