Sparks were definitely caused from the blades letting go and causing bending of the other blades rear of the initial damage. The blades then rub against the casing causing the sparks. It also appears from the image that the disc has failed big time and you can see its on a angle. I suspect that there was a disc failure which caused the large hole in the side of the engine. It is very lucky that it departed in that area and also I am wondering if there was enough velocity for the wing to be impacted? Has happened before. Its also interesting the amount of cra* that people talk on here.