DURHAM, N.C. — An internal Durham Police Department investigation involving officers into an alleged bar assault is "a black cloud" for the city and the police department, the city's manager said Tuesday.

"We need to remove it as quickly as possible," said City Manager Patrick Baker.

So far, five Durham police officers, and one who left the department, are under investigation for an alleged assault on a cook at a Raleigh sports bar last week. The men had gathered at the bar, sources said, for a going-away party for the sixth man. He had resigned from the department prior to the incident in question.

Rene Thomas, 29, told WRAL that he exchanged racial slurs with at least one of the men in the parking lot of Blinco's on Glenwood Avenue. He also alleges that one of the men also tried to punch him and that another kicked him.

Sources told WRAL on Tuesday that four of the officers accused -- Sgt. Mark Gottlieb, Gary Lee, Richard Clayton and J.A. Griffin -- were put on administrative duty last Friday. The fifth officer, Scott Tanner, was placed on administrative duty on Monday. Citing personnel issues, police would not say if their job-status change is linked to the internal investigation.

Gottlieb and Clayton, who are investigators in a high-profile rape investigation involving three Duke University athletes, as well as Griffin were questioned on Monday by Raleigh investigators.

So far, no charges have been filed in the case.

Baker said Tuesday that he is receiving daily updates about the investigation.

"We take professional conduct very seriously and professional conduct for police officers applies to them on-duty, off-duty, within their jurisdiction, outside their jurisdiction," Durham police Deputy Chief R. H. Hodge said on Monday. "We're going to investigate this matter and should we find there's some misconduct, disciplinary action will be taken."