Strong smell of gas inside 2012 Focus?

I have a 2012 Ford Focus. After driving at highway speeds (55 - 60 mph) for about 30 minutes and then stopping and turning off the engine there's a strong smell of gas inside the car. This doesn't happen for short runs around town at lower speeds. I've looked under the car and can't spot any signs of leakage. Anyone have any ideas what's going on?

Whatever it is, it isn't good.
You need to look under the hood while the car is running. Look for gas dripping from lines. Sometimes the clamps on the line are loose or a crack in the line itself.
One thing for certain is it should be found immediately.