Although your question is brief, it raises several "issues." First, you should certainly try to stop the harassment. Your Company should have a "no harassment" policy that sets forth the procedure to follow if (alleged) harassment occurs. Some sort of employee counseling and/or appropriate discipline should be held and issued.
Your company may be liable, depending on the facts and circumstances, such as the "harasser's" status as a supervisor, for example, and the availability of certain defenses.
I recommend contacting a local labor/employment attorney immediately to more fully review and assess your situation and help minimize your Company's exposure to liability.
No attorney-client relationship is created, or intended to be created, by this answer. You should contact an attorney licensed to practice law in your State for assistance in analyzing your specific situation.
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