Gaza police said on Wednesday that 55 children have been stricken by food poisoning at a UN school and seven of them are in critical condition. Police spokesman Islam Shahwan said the children ate food that passed its expiry date. There was no indication the incident was connected to Israel's closure of Gaza's border crossings. The school is run by the United Nations Relief and Works Agency (UNRWA), the body in charge of Palestinian refugees. The organization would not immediately comment. Shahwan said police were investigating whether the children were poisoned by food provided by the UN or by food they purchased from a shop.