CNN's New York offices were evacuated Thursday night after a bomb threat, but no explosive was found and police later gave the all clear, the network said.

The roughly 90 minute drama recalled a similar evacuation in October after an explosive device was discovered at CNN's New York headquarters.

Fire alarm bells rang inside the newsroom to signal an evacuation shortly after 10:30pm, CNN said on its website, as the network went to pre-taped programing.

An hour later the network was broadcasting from Skype.

"People just tuning in wondering why you're seeing me on Skype, why there's such technical difficulties, it's because we have been taken off the air because a bomb threat was called in to CNN," said host Don Lemon.

"We were evacuated and we know as much as you do."

"Due to a police investigation at Columbus Circle, West 58th Street between 8th and 9th Avenue is closed to vehicle and pedestrian traffic," the New York Police Department tweeted, referring to the address of the news organization's offices. "Please avoid this area. Update to follow."

Around midnight, CNN said police had given the all clear for people to go back into the building.

The bureau was previously evacuated in October after a package with an explosive device was discovered.

CNN was targeted amid a wave of pipe bombs sent to opponents of President Donald Trump.

A Florida man named Cesar Sayoc was arrested for allegedly sending them and was indicted on 30 federal counts. He faces up to life in prison if convicted.