Gag order placed on investigation into attack; massive traffic jams around Tel Aviv due to police checkpoints; explosion occurred just after noon, at corner of Shaul Hamelekh and Henrietta Szold streets; one casualty seriously wounded, one lightly-to moderately, and the rest sustain light injuries. A bomb exploded on a bus in central Tel Aviv at a little after noon Wednesday, wounding at least 28 people. As of Wednesday night six people were admitted to hospital overnight. Of these, three had surgery for moderate injuries that were described as not life-threatening, and three had mild injuries only. The remaining 26 people...