What causes the streaks in this photo?

In this photo of the Eyjafjallajökull volcano that is currently erupting, there are short, parallel streaks visible in the top left hand quadrant of the image, seemingly behind the bolts of lightning. What are these streaks?

My first thought was stars, but for stars to form such streaks the camera’s shutter must be open for several minutes, by which time the lightning would be blurred and faded. It cannot be debris from the volcano either, because they are so perfectly parallel and are exactly the same length, which implies the same velocity and trajectory for all these streaks. I am truly stumped here – can you please help me?