With a grand jury investigating and little support from House colleagues, Rep. Cynthia McKinney reversed course and apologized yesterday for an altercation in which she entered a Capitol building unrecognized, refused to stop when asked by a police officer and then hit him.

“I am sorry that this misunderstanding happened at all and I regret its escalation, and I apologize,” Ms. McKinney, a Democrat of Georgia, said during a brief appearance on the House floor. “There should not have been any physical contact in this incident.”

The grand jury investigation into whether to seek assault or other charges was continuing. It was unclear what impact the Ms. McKinney apology might have.

Her remarks came as two House officials who witnessed the March 29 scuffle prepared to answer subpoenas from the grand jury convened by U.S. Attorney Kenneth Wainstein. A day earlier, Ms. McKinney was shunned on the House floor by several colleagues, while the leaders of her party openly rejected her explanation that she was acting in self defense when she hit the officer.

What Ms. McKinney called a “misunderstanding” yesterday she had labeled “racial profiling” and “inappropriate touching” a day earlier. For nearly a week, she and her lawyers had insisted that she had been assaulted and had done nothing wrong. She is black and the police officer is white.

Ms. McKinney, 51, has a history of confrontations with officers.