The bridge was closed due to a pipe bomb threat, which was reported to be on the New Jersey side of the bridge, according to the police, cited by the New York Post.
Mayor Bill de Blasio announced on Twitter that the lanes of the bridge were closed due to a threat about a suspicious package.
New York City's official emergency notification system, all lanes of the bridge upper level were closed 9 p.m. (0100 GMT Friday) in both directions in The Bronx and Manhattan.
Due to police activity, all lanes of the George Washington Bridge upper level are closed in both directions in The Bronx and Manhattan. Consider alt routes. Multilingual & ASL Link: https://t.co/GpdlTK7FPB.— NYCEM - Notify NYC (@NotifyNYC) August 23, 2019
Some time after the threat came, the bottom lanes were reopened, but Bergen County Police and the Port Authority Police were investigating.