U.S. President Donald Trump said on Wednesday it may never be established who was responsible for an airstrike that killed more than 175 children and teachers at a girls’ school in Minab, southern Iran, on February 28, the opening day of the U.S.-Israeli military campaign against the country. Trump’s remarks came despite an internal U.S. military investigation that, according to a Reuters report, points to likely American culpability.

The Pentagon has elevated the probe but has not publicly confirmed any preliminary findings. Trump told reporters he had “seen nothing to lead me to believe it was” a U.S. missile, adding, “I don’t think it was us.” He claimed the truth may be obscured because “there were missiles flying all over the place,” and suggested accountability would remain elusive.

The president initially blamed Iran for the attack without providing evidence, before saying he would await an inquiry. The United Nations human rights office described the strike as “absolutely horrific” in the days after it occurred. Deliberately targeting a school would constitute a war crime under international humanitarian law, though U.S. officials have maintained that Washington does not intentionally strike civilian educational facilities.