N.J. Stat. Ann. § 2A:51-4

Any action instituted for the cancellation of a mortgage in the county in which the mortgaged real estate may be situate, shall, although the record of the mortgage so canceled may be in the county in which the real estate was situate at the time of the recording thereof, be as valid and effectual for the cancellation of the record of such mortgage in the county in which the same may be recorded, as if the proceedings had been instituted in the county in which the mortgage was recorded.