CAIRO, Aug 20 (Aswat Masriya) - A blast at the vicinity of a security building in Greater Cairo sent shock waves across the city in the early hours of Thursday, a security source said. 

The blast took place near the Homeland Security building in Shubra al-Khaima, at the northern tip of Cairo in Qalyubia governorate, a security source told Aswat Masriya.  

Rescue forces have moved to the neighbourhoods of Nasr City, Dokki and Imbaba, all densely populated residential neighbourhoods, security sources earlier told Aswat Masriya. 

The cause of the explosion remains unclear.

The blast has shaken houses in several neighbourhoods across the Cairo metropolis and sound of the blast has woken up residents.

Many residents immediately took to Twitter, to report hearing the sound, some even reporting shattered glass.

People on social media have reported hearing the explosion in the neighbourhoods of Dokki, Haram, Zamalek, Maadi, cental Cairo and even in outskirts of the city.