Gasoline Odor

I've got an 89 Ford Probe with 90K. it recently developed a gasoline odor. I checked under the car around the gas tanks and the gas lines. I didn't see or smell anything that would indicate a source.

What are some other possible sources?

Try looking with the engine running.
The fuel line may have a leak which only shows up when the engine is running when the fuel pressure in the line is at 35 psi.
Obviously be cautious about driving this car until its fixed.