Mysterious red light

I recently started to learn how to map for HL2 using hammer (big eeeech!). All is well except for one little problem: after i compile my map and start walking around in it in-game, i discover that certain faces are lit by a mysterious red light. Where that light is, i don't know. I've looked for it in the entity report but couldn't find such a light (the only lights in the map are blue and the light_environment is bright-orange). I don't use texlights since the map is an entirely outdoors one. Has anyone experienced this aswell?

Here's a pic of the problem.

Is there anything special about these "certain faces"? e.g. do they have overlays on top of them, or are displacement surfaces, have a certain texture you're using, etc.? What texture is that meant to be in that screenshot where it's gone red?

No, they are ordinary world brushes bearing the concretefloor001a texture. It only seems to happen to the sides of the brushes having this texture. That's why i thought it was a problem with the lights.rad, but after opening it i found that the problem wasn't there.