Police inspects the site of a sound bomb that exploded early Thursday at Ramsis train station in Cairo, November 20, 2014 (Photo: Al-Ahram)

People gather at the site of a sound bomb at Cairo's main train station in Ramsis Square, Egypt, November 20, 2014 (Photo: Al-Ahram)

Police inspects the site of a sound bomb that exploded early Thursday at Ramsis train station in Cairo, November 20, 2014 (Photo: Al-Ahram)

Police inspects the site of a sound bomb that exploded early Thursday at Ramsis train station in Cairo, November 20, 2014 (Photo: Al-Ahram)

People gather at the site of a sound bomb went off at Ramsis train station in Cairo, Egypt, November 20, 2014 (Photo: Al-Ahram)

The damaged windshield made by a sound bomb went off at Cairo's Ramsis train station, Egypt, November 20, 2014 (Photo: Al-Ahram)

People gather at the site of a sound bomb went off at Ramsis train station in Cairo, Egypt, November 20, 2014 (Photo: Al-Ahram)

The damaged windshield made by a sound bomb went off at Cairo's Ramsis train station, Egypt, November 20, 2014 (Photo: Al-Ahram)

Police inspects the site of a sound bomb that exploded early Thursday at Ramsis train station in Cairo, November 20, 2014 (Photo: Al-Ahram)