I see, I misunderstood. I've also dealt with a variety of other leaks. The most common is where flexible lines are cinch clamped to hard lines. In 3 different cases, I've had to cut the old cinch clamp off and replace with with a hose clamp with a screw. In the other case, it was an issue with my water heater leaking.
No matter what, you have to follow the water to the source. It's a real pain in the butt to do sometimes, though. What water fixtures are around the area that it's leaking? It could be a line feeding the toilet.
Often times you can remove panels from walls/cabinets in order to get a better look.