( CNN ) -- Explosions hit two metro stations and a courthouse in Cairo on Wednesday , injuring at least four people , state media reported . Two blasts went off at two different metro stations during the early morning rush hour , Egypt 's state-run Al-Ahram website said . The first explosion in the metro was caused by an improvised bomb at Shubra station , Al-Ahram reported , citing Interior Ministry spokesman Abdel-Fattah Othman . The second blast came from a `` sonic explosive '' in a trash can at Ghamra station , it said . The ministry spokesman denied earlier reports that explosions had gone off at more than two stations . Metro stations were reported to have been brought to a complete standstill as the ministry has declared a maximum alert . Another blast struck near the Heliopolis courthouse in eastern Cairo , Al-Ahram reported , citing eyewitnesses and local media . There was no immediate claim of responsibility for the blasts . Militants in Egypt have stepped up attacks since the military 's ouster last year of former President Mohamed Morsy , Egypt 's first democratically elected top leader . Last month , a spate of deadly explosions struck around the country , including one near a Cairo metro station .
NEW : A blast goes off near a courthouse in eastern Cairo , state media report . Minor explosions hit two different metro stations . Comment: