People being advised to allow for delays when travelling.

       National Highways reported the collision at 7.22am.

       By this time, traffic officers had arrived at the scene.

       Long queues soon developed back to at least junction 13.

       6.5 miles of congestion built up between junctions 15 and 16 alone, adding a minimum of 30 minutes to normal journey times.

       The collision was cleared to the hard shoulder in quick fashion, with reports following at 7.51am.

       But drivers are continuing to be warned to allow extra time for the congestion to clear.

       More to follow.