What are these hard spots in bananas?

My bananas have long hard spots going along the length of the fruit, inside the fruit, a couple millimeters below the surface, that is below the surface of the fruit not below the peel. It is not hard like an unexpected seed in some other plant, just harder than the rest of the banana. It goes along the length of the banana for around 5 centimeters from the bottom. It is like someone shoved a popsicle stick through them. It is shaped like a popsicle stick, flat and long. It is off center, that means not going through the center of the fruit, rather close to the surface. When peeled the problem cannot be seen without breaking the surface(like a bite). I do not mean soft brown spots. I do not mean the little deposit below the fruit opposite the stem.