Weird squiling noise... Cant figure out what it is

In the mornings when I start up my car, I let it warm up for about 10 to 15 minutes, then I get in and head to work. About 1/4 mile down the road a really loud annoying squiling noise starts happening, it almost sounds like its coming from somewhere in the dashboard...?
Its not my belt or anything,and I cant figure out what the hell it is.
Can anyone help?

mice ???

could it be the heater fan??