Rubber smell coming out of the engine compartment

My wife complained to me that smoke came out the engine, I got home and I drove it and accelerated and nothing happened, Today I drove it to the supermarket and I can smell burn rubber smell. I looked up in the engine, I can smell it but I don't see any evidence of burning, I don't know but is it maybe the belts need replacement, can some one tell me if could be something else.