I just bought a used 2009 Mazda5 GT with 68,000KM from a reputable Mazda dealership, and find this problem nagging me. When at 40-60km/h, if I press lightly on the gas peddle to accelerate a bit, I can hear a screeching sound coming from the front of the vehicle. It's not loud (I have very good ears), and it sounds like something spinning but the bearing is not lubricated. It only happens when I accelerate at this low speed range, and it seems to get louder when the engine is warm (after I've done some highway driving).

Any thoughts on the cause of this problem?

It's my first Mazda, and I've owned it for only a day. It might well be "normal" sound for this car.