Smoke coming out of seatbealt hole

What is your question?

Hello I have 1999 Corolla that has 150K miles on it and there is a burning smell that is coming out of the backseat seatbelt compartment, it smells like burning wax and it's coming from the middle seatbelt hole.

What makes this problem better or worse?

The smoke stops when the car is running but when it's stopped, it continues to spew out smoke.

How long has your 1999 Toyota Corolla had this problem?

A few days