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"We will not tolerate any form of hate speech, any expression that supports hate speech, or any acts of subversion, whether in-person or on online platforms," the department said in a statement Friday evening.
Though the department did not specify the nature of the social media accounts, it reiterated that hate speech will not be tolerated.
"The trust of our community is our highest priority. We will not tolerate any breach of that trust from any member of our Department," Interim Police Chief Susan E. Manheimer said.
The investigation comes after the department denounced the events that took place at the U.S. Capitol earlier this week, calling the riots "a disgraceful assault on our democracy."
On Thursday, the police department revealed a former employee of the department attended the Washington, D.C. riots.
Though the employee has not worked for the City of Oakland for six years, the department said, "We want to assure our community that those statements offend the morals and ethics of the women and men of our department."
As part of the internal investigation launched Friday, the Oakland Police Department said it will "root out" any conduct relating to the offensive social media content.
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The department said it is looking into whether any of its current employees violated department policies and city conduct codes.
"Our policies reflect the values of the Department and any employee found to violate these policies will be held accountable," the department's statement said.
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