Lebanon is in mourning and surveying the damage to its capital, Beirut, after a massive explosion ripped through the citys port and surrounding areas on Tuesday. At least 100 people were killed and 4,000 injured, with many still feared trapped under rubble.The cause of the blast, near the city's port, remains unclear. It was initially blamed on a major fire at a warehouse for firecrackers, the state-run National News Agency reported. The director of the general security directorate later said the blast was caused by "high-explosive materials confiscated years ago," but he did not provide further details.The explosion blew out windows in buildings across the city and could be felt as far as Cyprus, hundreds of miles away. A red cloud hung over the city as firefighting teams rushed to the scene.