A method of determining whether a page of NAND flash memory cells is in an erased condition includes applying a first set of read conditions to identify a first number of cells having threshold voltages above a discrimination voltage under the first set of read conditions, if the first number of cells is less than a first predetermined number, applying a second set of read conditions that is different from the first set of read conditions to identify a second number of cells having threshold voltages above the discrimination voltage under the second set of read conditions, and if the second number of cells exceeds a second predetermined number, marking the page of flash memory cells as partially programmed.