Two white flags have mysteriously replaced American flags on top of the Brooklyn Bridge in New York.
Images of the white flags - a traditional symbol of surrender - began appearing on social media, with many speculating about the significance of the removals.
There were suggestions that the flags were white-washed American flags.
Police have launched an investigation into the incident and work is now underway to replace the flags, the New York Post reported.
Brooklyn Borough President Eric Adams told ITV News that the stunt was no laughing matter with the bridge known to be a "high risk target".
"If flying a white flag atop the Brooklyn Bridge is someone's idea of a joke, I'm not laughing," Mr Adams said.
"The public safety of our city is of paramount importance, particularly our landmarks and bridges that are already known to be high-risk targets. We will not surrender our public safety to anyone, at any time.
"Political and social expression, whatever its message may be, has a place in our society, but not at the expense of others' security. I am confident in the NYPD's ability to investigate this matter."