A Livermore police officer has resigned in the continuing fallout from a sexual misconduct investigation that began in Oakland but grew to ensnare law enforcement agencies across and beyond the Bay Area over contact officers had with a teenage sex worker, officials said Thursday.

The resignation of the Livermore officer, who wasn’t identified, was announced the day after Oakland Mayor Libby Schaaf said the city was moving to fire four officers and suspend seven others at the conclusion of an internal affairs investigation.

The Oakland officers had attempted sexual assault, committed lewd conduct in public, assisted in prostitution and improperly accessed law enforcement databases, the internal review found.

Meanwhile, Livermore supervisors became aware June 14 of their officer’s sexual relationship with the 19-year-old woman, the daughter of an Oakland police dispatcher who goes by Celeste Guap, officials said. The officer was placed on administrative leave and handed in his resignation Sept. 2 at the conclusion of an internal affairs investigation. He will stay on duty until Sept. 16, said Livermore Capt. Jeramy Young.

“This incident does not accurately reflect the professionalism of the men and women of the Livermore Police Department who protect our community every day,” Livermore Police Chief Michael Harris said in a statement. “Now that this matter has reached a conclusion, we will move forward and continue to serve with honor and protect with purpose.”

Officials for other Bay Area law enforcement agencies said Thursday their investigations are ongoing and declined to comment.

A spokesman for the federal Defense Logistics Agency, however, said an employee, William Johnson, had been placed on administrative leave. Guap has said Johnson tried to pimp her out and showed text messages they exchanged to the East Bay Express.

Prosecutors in Alameda, Contra Costa, San Francisco and San Joaquin counties have yet to file criminal charges against the implicated officers and sheriff’s deputies, though Alameda County District Attorney Nancy O’Malley is expected to announce a decision soon, now that the Oakland investigation has concluded.

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The Oakland probe began last September with the suicide of Officer Brendan O’Brien, who left a note referring to Guap. Guap told The Chronicle that she had sex with O’Brien when she was 17 and that she had sex with 29 officers from multiple police agencies over the past two years.

Pamela Price, an Oakland civil rights attorney representing Guap, expressed frustration that no officer has faced criminal repercussions.

“It’s been 11 months since Officer O’Brien left a note exposing all of this,” she said in an interview last week. “Do criminals get charged 11 months after the fact? No, not normally.”

Kimberly Veklerov is a San Francisco Chronicle staff writer. Email: kveklerov@sfchronicle.com Twitter: @kveklerov