U.S. military investigators believe it is likely that U.S. forces were responsible for an apparent strike on an Iranian girls' school that killed scores of children on Saturday but have not yet reached a final conclusion or completed ​their investigation, two U.S. officials told Reuters.

Reuters was unable to determine more details about the investigation, including what evidence ‌contributed to the tentative assessment, what type of munition was used, who was responsible or why the U.S. might have struck the school.