Order, Family Court, New York County (Sheldon Rand, J.), entered on or about July 21, 1999, which granted the petition of the New York State Office of Children and Family Services for extension of respondent-appellant’s placement for a period of 6 months, unanimously reversed, on the law, without costs, and the petition dismissed.
It is uncontroverted that on July 2, 1999, when Family Court issued a temporary order extending respondent’s placement, his original placement had expired on June 16, 1999. Since the *72temporary order of extension was issued after the original placement had expired, Family Court lacked jurisdiction to extend the placement (see, Family Ct Act § 355.3 [1]; Matter of Wayne S., 193 AD2d 371, 373). Petitioner’s claim that it was not required to credit respondent’s placement with 16 days resulting from detention on an unrelated matter that was eventually dismissed (see, Executive Law § 510-b [7] [b]) lacks merit. Although petitioner asserts that it lacked knowledge of the dismissal, the record reflects that it was aware of respondent’s open case and was in fact tracking the matter while respondent was in its custody. Petitioner offers no explanation justifying its failure to ascertain the disposition of that case and credit respondent’s placement accordingly. Concur— Nardelli, J. P., Tom, Mazzarelli, Ellerin and Friedman, JJ.