Updated

U.S. Capitol Police are investigating an incident in which one of its officers allegedly tried to stop Rep. Cynthia McKinney, D-Ga., from bypassing a security checkpoint and ended up getting punched in the chest.

Capitol Police Sgt. Kimberly Schneider did not release any details surrounding the investigation, only saying that the "matter has been brought to their attention." But sources have told FOX News that the police action stems from the supposed confrontation Wednesday at the Longworth House Office Building on Capitol Hill.

According to the sources, McKinney was walking into the building at about 2:30 p.m. EST and went around the metal detector, which is customary for lawmakers.

The police officer apparently did not recognize McKinney and asked her to stop and walk through the metal detector. McKinney ignored the officer's requests more than once, the sources said, and the officer placed his hand on McKinney's shoulder.

The sources said that McKinney then turned around and hit the officer in the chest with her cell phone.

In a statement issued late Wednesday night, McKinney said the confrontation was "unfortunate."

"I was urgently trying to get to an important meeting on time to fulfill my obligations to my constituents. Unfortunately, the police officer did not recognize me as a member of Congress and a confrontation ensued. I did not have on my congressional pin but showed the police officer my congressional ID. I know that Capitol Hill Police are securing our safety, that of thousands of others, and I appreciate the work that they do. I deeply regret that the incident occurred," she said in a statement.

Dick Williams, publisher of the Dunwoody Crier, told FOX News that McKinney has often complained of mistreatment of African-American members of Congress regarding security checks on Capitol Hill. Indeed, this is not the first incident with McKinney at a checkpoint, according to Slate magazine.

"In August 1993, during her first term in office, a Capitol Hill police officer tried to prevent her from bypassing a metal detector, as members of Congress are allowed to do. For years afterward, The Hill reports, the Capitol Police pinned a picture of McKinney to an office wall, warning officers to learn her face because she refuses to wear her member's pin. (And because officers are innately suspicious of a black woman with braided hair and gold shoes)," reports the online journal.

A spokesman for House Speaker Dennis Hastert was quick to comment on the incident.

"On a day when the Democrats are promoting their national security agenda, it's probably not a good idea for them to allegedly strike police officers."

McKinney entered her sixth term in office in 2004 following a one-term hiatus. That came in 2002, when she was defeated in the Democratic primary after implying on a talk radio show that the Bush administration might have had advance notice of the Sept. 11, 2001, terrorist attacks. Her successor then sought the Senate seat, leaving the vacancy that allowed McKinney to return to win re-election.

FOX News' Molly Hooper contributed to this report.