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Order and judgment (one paper), Supreme Court, New York County (Charles Tejada, J.), entered on or about June 27, 2003, which denied the petition and dismissed the proceeding brought pursuant to CPLR article 78 to annul the determination of respondent New York State Division of Housing and Community Renewal, dated October 2, 2002, granting respondent owners' petition for administrative review and finding that the subject apartment was not subject to the city rent control law during the period of petitioners' tenancy, unanimously affirmed, without costs.

Having failed to oppose the owners' petition for administrative review, the tenants could not raise before the court the factual issues they claimed entitle them to rent-controlled status (see Matter of Steffey v New York State Div. of Hous. & Community Renewal, 276 AD2d 407 [2000], lv denied 96 NY2d 709 [2001]). The agency properly determined, based on its expertise in such matters and in the construction of the regulations it administers, that there had been a "substantial alteration" warranting decontrol.

We have considered petitioners' other contentions and find them unavailing. Concur—Tom, J.P., Ellerin, Lerner and Marlow, JJ.