Light in my house without a source

I built a pretty big house in minecraft pe, and it has a second level over half the house. The part under the second level is completely dark when there is no torches, but the second level as well as the half of the house not covered by a second level are lit up completely by themselves, as if there is no roof and it's just sunlight. There are no light sources anywhere in my house to cause this, and there are no windows to let sunlight in. Why is my house lit up?

It may have been there from a previous light source, as Minecraft does have glitches. If you exit Minecraft and reopen it, the glitch will most likely be fixed.