An underage sex scandal at Oakland Police Department is being investigated after several officers were accused of having sex with the same teenage girl.

The internal affairs investigation revolves around Celeste Guap, who allegedly had sex with more than a dozen police officers starting when she was 16, sources told KPIX5.

Guap, who is now 18 or 19 and lives in Richmond, California, started revealing details on Facebook suggesting she had illicit encounters with officers – calling the relationships ‘harmless’ but insisted that she did not ‘snitch’ on anyone.

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An underage sex scandal at Oakland Police Department is being investigated after several officers were accused of having sex with the Celeste Guap (left) starting when she was 16. Officer Brendan O’Brien (right) is reportedly one of the officers and left a suicide note that sparked an investigation

Guap has written on Facebook that the only officer she 'messed with' while underage is now 'gone'. She also shared a memory from a year ago (above) that hinted at an inappropriate relationship

This week, she posted on Facebook: ‘The only officer I ever messed with underage is sadly gone now, so I don't know why this is still being brought up.'

This is a reference to Oakland police officer Brendan O’Brien, 30, who committed suicide in September last year – around a year after his wife's death was also ruled a suicide, according to KPIX5.

O’Brien had left a note before his death that sparked an internal affairs investigation, the station reports.

His wife Irma Huerta Lopez died in June 2014 and her death was briefly classified by homicide detectives, according to the East Bay Express.

Her family believe O'Brien shot her and a coroner's report seen by the newspaper said her death was 'suspicious'.

The investigation into allegations of sexual misconduct was only opened after O'Brien's death on September 25, 2015, the Express reports.

But sources say sexual misconduct had been ongoing since 2014 and alleged that investigators may have failed to properly look into the allegations.

Guap, who is now 18 or 19, started revealing details on Facebook suggesting she had illicit encounters with officers – calling the relationships ‘harmless'

Just a few weeks ago, Guap shared a picture suggesting an Oakland police officer had dropped her off near her home in Richmond, California

Another investigation was later ordered by a federal judge, in which many officers admitted they had lied during the first one about their relationships with Guap.

One officer has reportedly now admitted having sex with Guap while knowing she was underage.

The officer, who has not been named, is facing a statutory rape charge in the criminal investigation that is also underway.

The current investigation involves three officers, police spokesman Johnna Watson said.

‘We are entrusted by the community to protect it, to serve them and to uphold the law,’ she told KPIX. ‘So we take the allegations very seriously.’

Daily Mail Online has contacted the department for further comment.

Guap has another connection to the department – her mother works as a dispatcher there. She has a tattoo on her decolletage that read 'Dios, Patria, Libertad' - which means 'God, Homeland, Liberty.'

Just a few weeks ago, the teenager posted a picture of an Oakland PD vehicle after claiming to have been dropped her off near her home, writing: ‘Took me back to Richmond in style.’