OAKLAND — An investigation of sexual misconduct involving three police officers and a woman surfaced in the wake of another officer’s suicide last year, authorities said Thursday.

Authorities obtained information while investigating the death of Officer Brendan O’Brien, and launched the sex-misconduct investigation, sources said.

O’Brien was 30 when he died on Sept. 25, 2015, in Oakland, according to the coroner’s office, which ruled his death a suicide. The San Francisco native’s wife also committed suicide in June 2014, authorities said.

Three police officers have been placed on paid leave due to allegations

of sexual misconduct between them and a female who does not work for the department, police said. They are also the subject of a criminal and internal affairs investigation.

The department has not named the officers, provided details about the allegations or said when the officers were placed on leave.

Sources said the officers initially contacted the woman through a social media site, and their other contacts with her were while they were off duty. The woman is related to a civilian employee of the police department, according to sources.

The law firm of Rains Lucia Stern is representing the three officers but declined to comment Thursday.

The case has upset U.S. District Judge Thelton Henderson, who oversees the department’s court-mandated reforms stemming from the 1999 Riders police brutality scandal.

“This case raises most serious concerns that may well impact defendants’ ability to demonstrate their commitment to accountability and sustainability — both of which are key to ending court oversight,” the judge wrote in a March 23 court order.

Civil rights attorney John Burris, one of the lawyers involved in the Riders case, also said the latest investigation could impact the department’s ability to end federal oversight, depending on what is found.

“It could be a setback,” said Burris, who called the latest case another “embarrassing” moment for the department.

In April, Officer Cullen Faeth was charged with four misdemeanors, including public intoxication, stemming from an attack on a probation officer at her Oakland hills home, on Dec. 7.

Rookie officer Matthew Santos was fired while on probation status for allegedly using a gun while off duty to threaten a man painting his apartment door in Emeryville on Feb. 17. He was charged in April with two felony counts.

In a statement released Wednesday, the department said it “will not tolerate misconduct of any kind from its employees. The (department) holds all employees accountable for their actions on and off duty.”

Staff writer Harry Harris contributed to this report. David DeBolt covers Oakland. Contact him at 510-208-6453. Follow him at Twitter.com/daviddebolt.