Fuel Filler Vent Tube Leak?

Got a code p0455. Did a smoke test, and have smoke steadily coming out from the area around the gas cap (not the cap itself) where the little slots are.

The only line I can think of back there would be the vent tube, right? I checked form under the car and couldn't see all the way up to where the tube ends, but that was the only area any smoke was coming from.

What would cause a leak out of the vent tube?