Durham, N.C. — The FBI could be called into a Durham Police Department internal investigation to determine whether police officers violated anyone's civil rights, authorities said Friday.

Several Durham police officers were placed on leave this week pending the outcome of the internal investigation. WRAL has learned the probe centers on allegations of sexual misconduct involving officers and prostitutes.

Police Chief Jose Lopez said Thursday that the allegations surfaced shortly after he took over the department in September. He said fewer than 10 officers, ranging from rookies to veterans, were involved, but he didn't reveal other details about the case.

FBI Supervisory Agent Greg Baker said Lopez called his office last week to talk about the evidence collected after a month-long internal investigation.

"He wanted to discuss their investigation, their findings thus far," Baker said. "I laid out the parameters of what may constitute a federal violation."

The FBI hasn't yet joined in the investigation, but Baker said the agency is on standby to determine whether any civil rights violations occurred.

"If the officer engaged in actions for personal gain under the official capacity as a police officers, using either coercion or threat" would constitute a violation, he said.

Lopez met with city officials for 30 minutes behind closed doors Thursday evening to brief them about the investigation after WRAL began asking questions about the case. He said he also has contacted prosecutors in the Durham County District Attorney's Office to determine whether any criminal charges are warranted.

Mayor Bill Bell said Friday that he has confidence in Lopez and didn't think the investigation would affect the police department's credibility.

Baker also noted that Durham police are being proactive in their investigation.

"Everyone's trying to do the right thing. No one wants this in their department," he said.