Palestinians in the Gaza Strip fired a Kassam rocket at the western Negev on Thursday, threatening to further derail an already shaky week-old truce. The rocket exploded in an open area near a Negev industrial zone. No one was injuried and no damage reported. The Fatah Al Aksa Brigades claimed responsibility for the attack. On Tuesday three rockets slammed into the western Negev, causing damage and lightly wounding two Sderot residents.In response to the rocket fire Israel shut down the crossings into Gaza. On Thursday the Sufa crossing, Karni's wheat conveyor belt and the Nahal Oz fuel terminal remained closed. Defense Minister Ehud Barak said earlier in the week that if the calm held Israel would hon