'08 Pathfinder AC making noises

My wife's '08 Pathfinder has developed a squealing noise after being driven a few miles. The rear blower has quit, and the noise persists. At first she told me that the rear fan was squealing, but now that it has quit, the squealing noise is still there. She doesn't indicate if fan speed is an issue or a variable in the squealing noise. sound or pitch.
I know I'm going to have to replace the rear fan motor, but what else would cause this squealing? I've not heard it myself as I seldom drive her vehicle.