radio speaker amplifier

Similar problem with my Toyota Camry. Driving to work one morning listening to radio and it suddenly went silent. I thought the radio station had problems. So I changed stations and it was still quiet. I loaded in a CD and it started playing (according to the display) but still no audio. So, all four speakers went silent at the same time and I can't find the cause. I've checked fuses and do not find a bad fuse anywhere unless it is hidden. Can'r find an audio amp anywhere. Not sure how to remove the radio to check connectors behind it.