WASHINGTON » District of Columbia police have opened an internal affairs investigation into statements made by an officer who responded to reports that singer Chris Brown had punched a man outside a Washington hotel.

That probe centers around a disputed conversation between the officer and an unidentified acquaintance of Brown, discrepancies that will likely be important to resolve as the criminal prosecution moves forward. The apparent inconsistencies are described in charging documents laying out the assault case against Brown and his bodyguard.

According to the police records, the acquaintance told detectives at the scene that the officer said Brown had never struck the alleged victim. The officer then denied even speaking with the acquaintance.

However, a uniformed Secret Service officer at the scene reported overhearing the conversation with the officer and confirmed the acquaintance’s story. And the accuser denied ever saying that Brown never struck him.

An Associated Press reporter who had previously asked the police department about that conversation was contacted this week by an internal affairs investigator assigned to the probe. The investigator confirmed a review was underway.

"We are aware of the discrepancy among witness statements in the Chris Brown case. This is not uncommon in cases with multiple witnesses involved. We have received no complaint of misconduct on the part of any officer in this matter," Police Chief Cathy Lanier said in a written statement.

The female police officer was not named in charging documents, and police officials did not identify her. The head of the police officers’ union said he had not been made aware of the investigation. Danny Onorato, Brown’s lawyer, declined to comment, as did a spokesman for the U.S. Attorney’s office, which is handling the prosecution.

Brown was charged with misdemeanor assault after a man said Brown and his bodyguard had punched him after he tried to get into a picture the singer was taking with two other people. His lawyer said he is innocent and revealed in court last week that he had rejected a plea offer. He is due back in court Feb. 20.

The internal affairs investigation could be important to the defense as the case moves forward.

At the time Brown was charged in Washington, the Grammy winner was on probation in California for a 2009 attack on singer Rihanna, his then-girlfriend. As a result of the new charge, a judge in December revoked Brown’s probation in California, but the ruling didn’t change a requirement that Brown complete rehab and community service including roadside cleanup and graffiti removal.