An explosion was heard near a state security building and courthouse in Cairo and may have caused casualties, Egyptian security sources said on Thursday, Reuters reported.
The cause of the blast was not immediately known.
Comments on Twitter suggested it was heard in several parts of the Egyptian capital.
State-run Al-Ahram newspaper reported an explosion occurred in Cairo's Imbaba district but gave no other immediate details.
Militants based in the Sinai who support the Islamic State group that controls parts of Iraq and Syria have previously claimed responsibility for attacks on security forces.