Egyptian official: Explosion outside Italian Consulate in Cairo damages building.

The Italian consulate shows heavy damage following a blast that killed at least one person in Cairo, Egypt, Saturday, July 11, 2015. An Italian embassy official said the consulate was closed at the time of the explosion and no staff members were injured. (AP Photo/ Mohammed el-Raai) (The Associated Press)

A crowd gathers outside of the Italian consulate following a blast that killed at least one person in Cairo, Egypt, Saturday, July 11, 2015. An Italian embassy official said the consulate was closed at the time of the explosion and no staff members were injured. (AP Photo/ Mohammed el-Raai) (The Associated Press)

A policeman stands at the base of the crumbled facade of the Italian consulate following a blast that killed at least one person in Cairo, Egypt, Saturday, July 11, 2015. An Italian embassy official said the consulate was closed at the time of the explosion and no staff members were injured. (AP Photo/ Mohammed el-Raai) (The Associated Press)

An Egyptian security official says an explosion has damaged the building housing the Italian Consulate in downtown Cairo.

The blast early Saturday morning caused extensive damage to the building's exterior and ruptured underground water pipes, flooding the area. The official said the exact cause of the explosion was still unclear, as was the extent of any casualties.

The explosion struck one of the busiest intersections in Cairo, a major artery that connects Ramsis Square to the heart of downtown Cairo. Even before 7 a.m. on a weekend in the middle of the Islamic fasting month of Ramadan, the area around the blast would have been crowded with cars, pedestrians and mini-buses.