Authorities are investigating after two white flags mysteriously replaced the Stars and Stripes on the Brooklyn Bridge this morning.

Read more from FoxNews.com below, and watch Trace Gallagher's report above.

John Miller, the city's deputy commissioner for intelligence and counterterrorism, said at an afternoon press conference that the lights illuminating the flags flickered around 3 a.m. just before the switch, and that the locks affixed to the gates on top of the bridge were still in place, suggesting that the perpetrators had a background in climbing training.

But the motive for the act remained unclear.

"At this time, it appears (the act) has no particular nexus to terrorism," Miller said. "This may be somebody's art project, or may be an attempt to make some kind of statement. But it's not clear what that statement is."

Miller said that security video shows that four or five people in a group, "and some other individuals," were seen climbing the bridge shortly after 3 a.m. Around 3:30 a.m., the light that normally illuminates the flag on the Brooklyn side of the bridge flickered, then appeared to go out. It appeared that aluminum pans were used to cover the lights.

He added that there was a 13-minute gap between the two flags going up, which he said was "suggestive" that two individuals, or two teams of individuals, were responsible.

"It looked like it had been thought out in advance," Miller said.

The white flags -- which appear to be American flags that were bleached white and measure 20 feet by 11 feet -- were discovered by construction workers around 5:30 a.m. They were removed around noon, authorities said earlier Tuesday.

White flags are a universal sign of surrender. Miller said whether the decision to use bleached American flags was a statement of patriotism or defiance was "up for everyone's interpretation."

NYPD Commissioner William Bratton said "he's not particularly happy about the event," and said police were seeking the public's help in finding suspects. Miller added that police are combing social media to see if anyone took credit for the switch.

Mark S. Weprin, a city councilman, posted a photo of the white flag on his Twitter account. He wrote, "Why are there white flags on top of the Brooklyn Bridge?"

Brooklyn Borough President Eric Adams told The New York Post that security for these high-risk targets is a top priority for law enforcement.

"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," he told the paper.

The city's Department of Transportation, which operates the bridge, referred all queries earlier Tuesday to the NYPD.