"We are working with Capitol Hill police to fully understand and appreciate the incident," principal assistant U.S. Attorney Channing Phillips told The Associated Press in a telephone interview.
Citing a continuing investigation, Phillips would not say whether the referral included a recommended charge against the six-term Democrat or when a warrant for her arrest might be issued.
In a statement, Capitol Police said it "has referred its investigative findings to the U.S. attorney." The department must obtain approval from U.S. Attorney Kenneth L. Wainstein before it can ask a judge to issue an arrest warrant on assault or other charges.
McKinney spokesman Coz Carson acknowledged the investigation.
"We're aware that the wheels are turning in Washington," Carson said. "We have no control over what they decide to do. We will make the appropriate statement and take the appropriate action once we know where they're going."
For her part, McKinney said she expects to represent her constituents in the suburbs of Atlanta, Georgia, for many years.
"Rest assured, I am doing the work they sent me to Washington to do. Nothing is going to keep me away from my responsibilities," McKinney told a crowd of supporters in Atlanta on Monday.
McKinney, 51, scuffled with a police officer on March 29 when she entered a House of Representatives office building without her identifying lapel pin and did not stop when confronted. Several police sources said the officer, who was not identified, asked her three times to stop. When she kept going, he placed a hand somewhere on her and she hit him, according to the officials, who spoke on condition of anonymity.
McKinney, who is black, issued a statement of regret for the incident but no apology. At a press conference Friday, she and her lawyers declared that she was a victim ofand said they were considering pursuing civil action against the officer.
Black clergy members and lawmakers came to the defense of the firebrand congresswoman on Monday. McKinney smiled as her supporters heaped praise on her leadership and her new look, her trademark cornrows hairstyle replaced this year by a curly brown afro.
McKinney's supporters tried to minimize the incident — which they called political, not criminal — but they also suggested it constituted racial profiling by the officer. They called publicity surrounding the episode a distraction that is being used by "her enemies" to keep the congresswoman from performing her elected duties.
The Rev. Reverend Darrell D. Elligan, president of Concerned Black Clergy in Atlanta, called McKinney competent, courageous and committed.
"She has our support unconditionally," Elligan said. "She is not a threat to the security of our country."
Also on Monday, Atlanta's WSBTV reported McKinney admitted she broke government rules by spending about $1,000 of taxpayer money to fly singer Isaac Hayes to Atlanta to help dedicate a new office. The money came from a fund members of Congress are supposed to use for office supplies.