GAZA, July 30, 2008 - An explosion has hit a Hamas training camp in southern Gaza, Palestinian health officials said on Wednesday. According to eyewitnesses, the explosion late on Tuesday completely destroyed the command center of Izz el-Din al-Qassam Brigades, the military wing of the radical Islamic movement Hamas. The blast was heard all over the southern city of Khan Younis. A second, less powerful explosion followed some 15 minutes later. The exact number of casualties is currently unknown. According to Palestinian health officials, two people have been injured, while local media puts the number of casualties at five or six. The cause of the blast is as yet as unknown, and neither Hamas nor Israeli officials have commented. The training camp, located in a former Israeli settlement, had already seen a deadly explosion earlier this month. On July 8, a blast at the camp's training facility killed two militants and injured three. Izz el-Din al-Qassam Brigades said in a statement that the two victims had been preparing to carry out a "holy mission," but the explosives had detonated prematurely. Israel and Palestinian militants signed a Gaza Strip truce on June 19.