Who switched Brooklyn Bridge flags?

• Mysterious white flags are spotted atop the Brooklyn Bridge rush hour Tuesday


• NYPD's Counter-Terror Bureau and Intelligence Division are called to the bridge


• NYPD detective to CNN: "Perhaps more security is needed"

(CNN) -- The NYPD is investigating how two American flags that fly at the top of the Brooklyn Bridge were replaced by two white flags.

The swapped-out flags were spotted by construction workers at 5:30 a.m. Tuesday, NYPD Deputy Commissioner for Intelligence John Miller said at a news conference Tuesday afternoon.

He said members of the Emergency Service Unit found two flags, one on each tower of the bridge, that appeared to be American flags that had been bleached white. The workers also found large aluminum pans affixed as covers over the lights and secured with zip ties, Miller added.

The NYPD's Counter-Terror Bureau, the Intelligence Division and the Emergency Service Unit were on the bridge as the white flags were removed, according to an NYPD detective.

Brookly Bridge construction workers found large aluminum pans covering the lights, police say.

"At this time, it appears it has no particular nexus to terrorism or even politics," Miller said. "This may be somebody's art project, or it may be an attempt at making some kind of statement, but at this point it's not clear what that statement is."

NYPD Police Commissioner Bill Bratton called the incident a matter of concern and said that police are requesting the help of the public as they continue to look across social media for claims of responsibility.

Miller said that the NYPD has video that shows a number of people crossing the bridge just after 3 a.m. Tuesday and within the hour, the light that normally illuminates the flag on the Brooklyn side of the bridge flickered and appeared to go out and a few minutes later the same thing occurred on the Manhattan tower.

Miller added that he believes the bleached flags were made at home and that whoever did this might have had some climbing or construction experience.

"There is a standard level of security at the bridge; apparently that security failed this morning or last night. Perhaps more security is needed," a NYPD detective familiar with the investigation said.

Miller said that there are two NYPD vehicles at each end of the bridge at all times, and after the news conference told reporters that the department is looking at putting NYPD cameras on the bridge.

Should the incident just prove to be a stunt, some people don't find the humor.

"If flying a white flag atop the Brooklyn Bridge is someone's idea of a joke, I'm not laughing," Brooklyn Borough President Eric Adams said in a statement. "The public safety of our city is of paramount importance, particularly our landmarks and bridges that are already known to be high-risk targets."

Adams announced at a news conference Tuesday that he is offering a reward of $5,000 for information leading to the arrest of the person or people responsible.

New York City Councilman Mark Weprin tweeted a photo of the flags Tuesday morning. "I drive over the Brooklyn Bridge often, I thought, what the heck is that about?" Weprin told CNN. "I'm curious and I'm also concerned if it was vandals."

The Brooklyn Bridge opened in 1883 and at that time was the longest suspension bridge, according to the Department of Transportation.

It has been designated a National Historic Landmark by the National Park Service, and a New York City Landmark by the Landmarks Preservation Commission.

CNN's Sonia Moghe and David Shortell contributed to this report.