Smoke coming out of subs

If smoke has come out of the subwoofer, the speaker itself, that means the voice coils have been heated excessively and they are damaged or in this case, I'd say completely blown. Voice coils blow because they've been driven too hard, too much power, too much distortion for too long.

If you can get access to the front of the subwoofer speakers, gently put even pressure with your fingers near the middle of the cone, just around the edge of the centre dust cap and push gently and slightly inwards. If you hear or feel a "scratchy" type sound or feel, or if they dont move in freely, they are blown. And if that's the case, your amp could be damaged as well.

Most modern car amps have circuit protection and will shut down when they detect a load greater than they are used to so the amp MAY be ok. One way to test the amp is to hook another speaker to it, any speaker as a test is ok, and see if sound comes out. Make sure all power is off when connecting and disconnecting speakers!