JERUSALEM (AP) – Israel says it is massing troops along the Gaza frontier and calling up 9,000 reservists ahead of a possible ground invasion of the Hamas-ruled territory. Egyptian mediators rushed to Israel for cease-fire efforts but showed no signs of progress. The stepped-up fighting came as communal violence in Israel erupted for a fourth night. Jewish and Arab mobs clashed in the flashpoint town of Lod. The fighting took place despite a bolstered police presence ordered by the nation’s leaders. The four-day burst of violence is the most intense fighting Israel has ever had with Hamas. It has also sparked the worst Jewish-Arab violence inside Israel in decades.