Unfortunately for you, the property manager is your agent and the prospective tenants reliable on his authority and apparent authority to contract and make agreements for you. So, you "might" be stuck with the lease agreement and accepting the tenants in the residence.
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Mr. Leroi is correct; but as he implied your liability for breaching the lease (i.e. preventing move-in) depends upon the terms of the lease agreement. You will need to have an attorney review the lease agreement for a definitive answer. I would also add that if you do not have power of refusal in the management agreement then you should retain an attorney to review and re-negotiate the management contract. The management company wants to make money by keeping the property occupied - they are not be concerned about protecting your assets so you should retain authority for final approval of tenants.
This response is for general purposes only and does not create an attorney-client relationship.
I presume that the relationship you have with the property manage involves a contract that gives you final say in determining who any eventual tenant is allowed in the property. If not, that's a problem and a lesson learned.
Bring any and all applicable paperwork to the office of an experienced landlord/tenant attorney to make sure your options are fully understood.
In no way am I offering you legal advice, and in no way has my comment created an attorney-client relationship. You are not to rely upon my note above in any way, but insted need to sit down with counsel and share all relevant facts before receiving fully-informed legal advice. If you want to be completely sure of your rights, you must sit down with an experienced criminal defense attorney to be fully aware of your rights.