UNITED NATIONS (AP) — The U.N. secretary-general on Wednesday said he was “alarmed” to hear that rockets were placed in a U.N.-run school in Gaza and now “have gone missing,” and he demanded a full review of such incidents.

A statement by the spokesman for Ban Ki-moon expressed the U.N. chief’s “outrage and regret” at the placement of weapons at a site run by the global organization. The U.N. says that has happened at least twice so far in the current fighting.