MIAMI, FL - OCTOBER 21: Gerald Henderson #12 of the Philadelphia 76ers looks on during a preseason game against the Miami Heat at American Airlines Arena on October 21, 2016 in Miami, Florida. (Photo by Mike Ehrmann/Getty Images)

MIAMI (AP) — A woman performing the national anthem before an NBA preseason game in Miami on Friday night did so while kneeling at midcourt, and opening her jacket to show a shirt with the phrase “Black Lives Matter.”

The singer was identified by the Heat as Denasia Lawrence. It was unclear if she remained in the arena after the performance, and messages left for her were not immediately returned.

Heat players and coaches stood side-by-side for the anthem, all with their arms linked as has been their custom during the preseason. Many had their heads down as Lawrence sang, and the team released a statement saying it had no advance knowledge that she planned to kneel.

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“We felt as a basketball team that we would do something united, so that was our focus,” Heat coach Erik Spoelstra said. “Throughout all of this, I think the most important thing that has come out is the very poignant, thoughtful dialogue. We’ve had great dialogue within our walls here and hopefully this will lead to action.”

The anthem issue has been a major topic in the sports world in recent months, starting with the decision by San Francisco 49ers quarterback Colin Kaepernick to not stand for its playing. Kaepernick cited racial injustice and police brutality among the reasons for his protest, and athletes from many sports — and many levels, from youth all the way to professional — have followed his lead in various ways.

“All I can say is what we’ve seen in multiple preseason games so far is our players standing for the national anthem,” NBA Commissioner Adam Silver said in New York earlier Friday, at a news conference following the league’s board of governors meetings. “It would be my hope that they would continue to stand for the national anthem. I think that is the appropriate thing to do.”

The NBA has a rule calling for players and coaches to stand during the anthem.

Heat guard Wayne Ellington often speaks about the need to curb gun violence, after his father was shot and killed two years ago. He had his eyes closed for most of the anthem Friday, as per his own custom, though was aware of Lawrence’s actions.

“At the end of the day, to each his own,” Ellington said. “If she feels like that’s the way she wants to stand for it, then more power to her.”

Making a statement in the manner that Lawrence did Friday is rare, but not unheard of in recent weeks.

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When the Sacramento Kings played their first home preseason game earlier this month, anthem singer Leah Tysse dropped to one knee as she finished singing the song.

Tysse is white. Lawrence is black.

“I love and honor my country as deeply as anyone yet it is my responsibility as an American to speak up against injustice as it affects my fellow Americans,” Tysse wrote on Facebook. “I have sung the anthem before but this time taking a knee felt like the most patriotic thing I could do. I cannot idly stand by as black people are unlawfully profiled, harassed and killed by our law enforcement over and over and without a drop of accountability.”