CAIRO, Aug 14 (Reuters) - An electrical fire swept through an Egyptian Coptic Christian church during Mass on Sunday, causing a stampede and killing at least 41 people, most of them children and many suffering from smoke inhalation. The blaze started just before 9 a.m. in the Abu Sifin church in the city of Giza where about up to 1,000 people had gathered. The fire blocked an entrance to the church, causing the stampede, the two sources said, adding that most of those killed were children.