Pipe bombs were intercepted after they were addressed to former US President Barack Obama, former Secretary of State Hillary Clinton, former President Bill Clinton, and CNN’s headquarters in New York.
The devices are believed to aimed at high-profile Democrats.
US President Donald Trump has voiced his outrage over the suspected explosive devices, saying acts of political violence have “no place” in the United States.
It is reported that the serial bomber is suspected of sending at least five mail bombs.
The device has an envelope attached, filled with white powder.
In response, the NYPD bomb squad closed down parts of Manhattan, placing it into lockdown as they moved a pipe bomb-style device from CNN’s New York office to detonate it at its Bronx headquarters.
“This clearly is an act of terror attempting to undermine our free press and leaders of our country through acts of violence,” New York Mayor Bill de Blasio said.
“The very concept of terrorism is to change us and we will not allow that to happen.”