Whistling noise, then smoke pouring throught the car vent?

I have a 94 ford explorer. I was driving down the road and all of a sudden heard a whistling noise. I smelled a burning smell, but the engine wasn't anywhere near hot. And then i turned the heat off. It had been on low. The whistling stopped about 10 seconds later. I turned the heat back on and smoke poured into the vehicle from the vents. What is wrong with it?

Eject, eject. Sounds like the heater fan motor has bit the dust.

Could be the Freon from the air conditioner. Try the a/c does it blow cold air? Does the blower motor still blow air out of the vent? Maybe blower but i'm thinking that a seal from the air conditioner blew