Essex Police is reviewing procedures after its own Facebook page was found carrying a string of racist comments.
The constabulary placed an appeal about smashed windows at Southend Mosque on its Facebook page.
But within hours more than 20 racist comments had been published and left for days without being removed.
A spokeswoman for Essex Police said it was investigating the matter, including whether the force, in running the page, had breached the law.
She said the comments were "completely unacceptable" and said the police had not encountered such problems before.