CNN knocked off the air after bomb threat forces evacuation at NYC's Time Warner Center
Poppy Harlow and Jim Sciutto (CNN)

CNN was momentarily knocked off the air after a suspicious package forced the evacuation of its New York City headquarters during a live broadcast.

Anchors Poppy Harlow and Jim Sciutto were reporting on explosive devices mailed to former presidents Bill Clinton and Barack Obama and billionaire financier George Soros this week when a fire alarm sounded.

The confused anchors interrupted a guest and said they were being forced to evacuate, and CNN returned from a commercial break with an update from its Washington bureau.

Police and firefighters were called to the Time Warner Center to investigate the suspicious package.

The manila envelope affixed with six stamps was addressed to former CIA director John Brennan, who is now a CNN contributor and an outspoken critic of President Donald Trump, law enforcement sources told TMZ.