Theories abound over two bleached American flags planted atop the Brooklyn Bridge, but the whodunit has the NYPD stumped. Reuters

As New York Police Department investigators labor to figure out who's responsible for placing bleached-white American flags atop the Brooklyn Bridge on Tuesday, the Internet and social media have run amok with some interesting explanations.

White flags, of course, are popularly associated with surrender, and more than a few media outlets have had fun with that allusion. "Hipsters Surrender," the front page of the New York Post proclaimed.

But maybe it's the other way around. Rebecca Mead, a writer for the New Yorker, joked that the flags represented "Manhattan surrendering to Brooklyn."

Maybe the perpetrators wished to indicate Brooklyn's surrender to gentrification, or surrender by the U.S. government, or surrender of the country's standing in the world. At this point, anything's possible.

Perhaps surrender wasn't the point at all. Some astute art connoisseurs noted that the Neo-Dada artist, Jasper Johns, was fond of painting American flags, and several of his works depict white American flags. But the 84-year old artist isn't particularly known for guerilla art projects. Banksy, on the other hand, is, and several Twitter users suggested perhaps the famous anonymous artist/activist was behind the white flag stunt.

White Flag is also the name of a 1980s California punk band. The website 2Paragraphs -- which condenses notable news stories down to an easily digestible two paragraphs -- amusingly postulates that the flags are a clever plug for a new White Flag album. But White Flag's leader, Pat Fear, passed away in September 2013, as Spin magazine reported.

2Paragraphs has some other interesting observations, including one particular connection between the white flags and an American literary classic:

"The white flags on the Brooklyn Bridge are an homage to Melville's incomparable chapter 42 in Moby Dick, The Whiteness of the Whale. (Moby Dick is 163 years old, the flags are approximately 163 centimeters tall, Melville once worked downtown near the bridge.)"

Several comment threads devoted to the white flag mystery have cropped up on Reddit pages that explore conspiracies. Given that the Brooklyn Bridge is a high-profile terrorist target, one Redditor suggested the flags could be the beginning of a larger art project to symbolize the "theater of safety," whereby placing white flags near major landmarks serves as a way to expose their true vulnerability.

That last point, in fact, speaks to the most concerning element of the mystery, regardless of who's behind it. And jokes about hipsters aside, police are taking the security breach seriously. Video footage shows unidentified people walking on the bridge's footpath at 3:10 a.m. and 3:30 a.m. on Tuesday morning before the lights at the bridge's tower went dark. Officials said the perpetrators likely had knowledge of climbing or bridgework, and may even have scaled the famous landmark before, the Associated Press reported.

John Miller, the NYPD's deputy commissioner, stressed that the stunt didn't appear to be terrorism related. "This may be somebody's art project or an attempt to make some sort of statement," Miller said. "But at this time it's not clear what that statement is."

Or maybe all investigators need to do is start looking up:

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