Lots of possibilities, as this point is low on the engine, so anywhere above can cause it!
Need to clean it up with gunk and hose, then see where it is originating.
I had same symptoms, and turned out to be camshaft oil seal. Only noticed it by drips on the drive, and oil filter housing was covered in oil.
Cleaned it, then followed it up to the cam belt end of the camshafts.