An NYPD station house in Brooklyn is under fire for its display of a black-and-white American flag with a thin blue line streaked through its center, a controversial symbol seen by many as a repudiation of the Black Lives Matter movement.

A photo of the "thin blue line" flag was shared with Gothamist/WNYC by an anonymous tipster, who said he first noticed it around two weeks ago outside the NYPD's Highway Patrol station on Flatbush Avenue. The flag, he said, is hoisted directly below the station's American flag, and visible from the Belt Parkway.

"I've noticed that it comes and goes," said the tipster, who requested we not share his name because he feared professional consequences. "I was upset and I was surprised. Several police departments have banned it...and I would've guessed the NYPD was among those to have such a policy."

A spokesperson for the department would not comment on whether there is an official prohibition on flying the flag, saying only: “The commander of our NYPD Highway district is looking into the matter."

The flag had not yet been removed as of Wednesday afternoon—hours after we initially asked the NYPD for comment.

Proponents of the symbol say it should be viewed as a show of solidarity with law enforcement, and that the line is intended to represent the separation of chaos and civilian life maintained by police officers. It's become closely associated Blue Lives Matter, a pro-police countermovement that arose in opposition to Black Lives Matter.

In recent years, white supremacists and neo-Nazis have also adopted the flag, which featured prominently at the deadly "Unite the Right" protest in Charlottesville. Since then, it's become a flashpoint at state capitols and police precincts throughout the country.

Earlier this month, county officials in Maryland ruled that a handcrafted flag should not be hung in a local police station, due to its divisiveness. Governor Larry Hogan, a Republican, then got involved, calling the decision, "disgraceful."

Similar controversies have played out in Oregon, Connecticut, Maine, and California—with varying outcomes. In Connecticut's capitol building, a plaque emblazoned with the symbol was briefly taken down, but subsequently restored following outcry from the law enforcement community.

A spokesperson for Governor Andrew Cuomo did not respond to a request for comment on whether the flag belongs on New York police property. The Mayor's Office directed us to the NYPD.

Hawk Newsome, president of Black Lives Matter of Greater New York, called for the flag to be taken down immediately.

"This thin blue line flag has the same optical impact on many of us as the Confederate flag," he told Gothamist. "It is a symbol of oppression."

Additional reporting by Fred Mogul.