Secretary of State Antony Blinken will return to Israel on Monday as the country prepares to launch an invasion into Hamas-controlled Gaza by air, land and sea, State Department spokesman Matthew Miller said Sunday. Hundreds of thousands of people in northern Gaza are fleeing in buses, in cars and on foot, crowding onto narrow roads leading south after Israel’s evacuation warning. Rear Adm. Daniel Hagari, a spokesman for the Israel Defense Forces, said Sunday that about 600,000 people had evacuated south and that others should follow. The Israeli military said it is preparing a “wide range” of offensive plans “for the next stages of the war, with an emphasis on significant ground operations,” though it has not provided a concrete indication of when the assault would start. So far, 30 Americans have been killed in Israel and 13 U.S. nationals are unaccounted for, the State Department confirmed Sunday. Officials did not respond to questions asking whether any Americans have been killed in Gaza, where there are an estimated 500 to 600 Palestinian Americans.