Egypt’s police tightened security after authorities found two bombs near the arrival hall of the city’s main airport while a homemade explosive was set off in central Cairo earlier Tuesday, Reuters reports, citing security sources. The airport bombs were discovered using electronic devices, but no arrests were made. Airport security was looking at surveillance footage, the sources said. The target for the explosion near a busy square in central Cairo was not immediately clear. Islamist militants have carried out a number of bomb attacks on security forces since the army ousted the President Mohammed Morsi of the Muslim Brotherhood in 2013.