Duluth police received a number of donated masks depicting the "thin blue line flag" — a black-and-white U.S. flag with a single blue stripe — this spring, likely March or April, at which time they were made available, according to Ingrid Hornibrook, the department's public information officer. The masks are black on the reverse side.

"We made the suggestion to officers that we should probably flip them around so that just the black side was showing. And then, some did and some didn't because it wasn't an order or a directive or anything like that," she said.

Hornibrook reports a number of officers used the masks without incident until Tuesday, when several complaints were lodged.

"So then yesterday, we reminded officers and employees to wear it black side out," she said.

Some of the complaints that rolled in Tuesday involved claims that officers were wearing "blue lives matter" masks.

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"We took it seriously, got back to every single person, talked to them on the phone and found out at which incidents they had seen the 'blue lives matter' masks," Hornibrook said.

The department then went back to review body camera video from the reported dates, and Hornibrook said they found no footage of officers wearing masks with the words: "blue lives matter."

Many people consider the black-and-white flag with a blue line to be a show of support for law officers and a sign of respect for those who have fallen in the line of duty. But the same flag has been usurped by white supremacists and is sometimes wielded as a counterpoint to the Black Lives Matter movement.

Andrea Gelb wrote to share her concerns about the masks with Duluth city councilors, noting: "There are law enforcement agencies across the country that have banned the internal use of the blue line flag because it's become a divisive symbol. One of those current interpretations is that it does symbolize 'blue lives matter.' Another interpretation is that it references the blue wall of silence."

Hornibrook doesn't personally consider the "thin blue line" flag insignia offensive and has worn a mask bearing that image herself. But she said: "We're a police department for all. So, when we hear that a certain image or something like that may be offensive to a certain group, we certainly take that seriously and make adjustments along the way, whether it's wrongly associated or not."

Hornibrook went on to say: "There's been the suggestion that the 'thin blue line flag' is associated with white supremacy, and that's just not the case. But it's up to us to listen to the citizens that we are sworn to keep safe and make sure that they feel safe and comfortable while interacting with our officers."

New navy blue masks that match uniforms are now on order for the Duluth Police Department, Hornibrook said.