Eds: UPDATES with health official saying three children killed GAZA CITY, Gaza Strip (AP) _ Three Palestinian children were killed Wednesday in a blast in northern Gaza, a Palestinian health official said. Witnesses said an Israeli tank shell exploded near Beit Hanoun. The Israeli army said it would look into the report. Dr. Muawiya Hassanin of the Palestinian Health Ministry said a girl and two boys were killed. He did not have their names or ages. 291430 aug 07GMT