Wow, that is scary! If you can't find the source, you need to get a friend or a RV tech to check it out for you. If it's not the fuel line to the generator, that leaves the fuel line to the engine. Follow your nose!
A friend with another brand Class C had loose screws in the frame around the gas filler cap. His fill tube was loose and the check engine light came on. He's replacing the screws with bolts. Be sure to check your filler tube.
Only some of us learn by other people's mistakes, the rest have to be the other people!