GENEVA, March 17 (Reuters) - A U.N. inquiry has started investigating a ​fatal strike on a primary school on ‌the first day of U.S.-Israeli attacks on Iran, one of its members told reporters on Tuesday.The attack on the Shajareh ​Tayyebeh School consisted of two missile strikes ​in quick succession that killed 168 children, mostly ⁠girls, Iranian officials said in Geneva on Monday.The Reuters Iran Briefing newsletter keeps you informed with the latest developments and analysis of the Iran war. Sign up here.Reuters ​reported on March 5 that U.S. military investigators believe it ​is likely that U.S. forces were responsible but have not yet reached a final conclusion or completed their investigation. The Pentagon ​has since elevated the probe."We're at an early stage ​of that investigation," Max du Plessis, a member of the ‌U.N. ⁠Fact-Finding Mission on Iran, told a Geneva press conference, saying that it had credible reports backing Iran's death toll."It's clear to us that whatever happens in ​respect of such ​an event, ⁠given the innocent lives that have been lost, there is a critical need ​for such an investigation to be done ​and ⁠for an independent outcome to follow," he said.If U.S. fault is confirmed, it would rank among the worst ⁠incidents ​of civilian deaths in decades ​of U.S. military strikes in the Middle East.Reporting by Emma Farge; Additional ​reporting by Olivia Le Poidevin; Editing by Miranda MurrayOur Standards: The Thomson Reuters Trust Principles., opens new tab