If toyota warranty doesn't cover it then try replacing the belt. I had that problem a few weeks ago. The car just started squeeling like crazy and it gets louder and louder. It's just like the brakes, the metal things on the pads start rubbing against the rotor or drum, telling you that it's time to change the pads. The same sort of thing happens with the belt, it tells you thit you need a new one. When I took my old belt there were little piecies of glass or something in it and the new one that I bought was clean on the inside. When the belt gets worn to a certain poin those glass things start to come out and they make that squeeling noise. I took a part every pulley and there were no signs of any of them rubbing against anything and the bearings were good. I thought it was the alternator, but the mechanics at a local garage told me that my alternator was OK. Finally went to the dealership, they wanted to charge me a $100 (canadian) for just an inspection + labour + the belt. I bought the belt for $20 (canadian) at a local automotive store. I'm pretty sure that they know what was squeeling. Last time I was at that dealership I heard two cars with the same problem, one was a solara and another was a camry.
If it's not covered under warranty, either try to change the belt by yourself or go to a good shop and have them do it, (it will be much cheaper) insted of going to the dealership.