The building was evacuated in the middle of Don Lemon's live show, the anchor said.
A preliminary search by security found nothing, and the NYPD was conducting a search as a precaution, the police official said.
This was the third time that CNN had faced an evacuation over bomb threats.
CNN's NY offices and studios have been evacuated due to a phoned bomb threat, the company says. "NYPD is going through our building", Lemon said, pointing to police officers lined up down the block, about 100 feet from the entrance of the building. "All of the employees, all the people who were in the building as we were doing our live broadcast are out of the Time Warner Center now".
Members of the NYPD's Emergency Services Unit swept the building and gave the all-clear shortly after midnight, reopening it for occupation.
China's State Media Offers Some Clarity on U.S. Trade Deal
China's Ministry of Commerce did not respond to phone calls and a faxed request to comment. President Donald trump and Chinese President XI Jinping was successful.
Initial reports conflicted about the precise time of the bomb threat itself, raising questions about whether Trump's tweet might have instigated the attack.
In October, Time Warner Center was evacuated after a package containing an explosive device addressed to ex-CIA Director John Brennan was discovered.
Within the same hour as the bomb threat, President Donald Trump, who has made a political career of attacking CNN, had just tweeted about "fake news".
A Florida man named Cesar Sayoc was arrested for allegedly sending them and was indicted on 30 federal counts.