Pictures would certainly help, plus more info...ie, is it a portable gas tank, is it permanent, doesbthe fuel line run under the floor, is the floor foamed in, or is it that someone spilled gas and saturated the foam?
Well the line is ran from two portable tanks in a storage compartment in the front to the back. The line is ran in the bottom with foam on top of it for floor support.
So the hose is the most likely culprit. Not knowing how long that hose has been there, Id replace the whole hose with a marine approved hose. Im not a fan of splicing when it comes to those.