U.S. President Donald Trump said on Wednesday that it may never be known who was responsible for an air strike that killed more than 175 children and teachers at a girls’ school in Minab, southern Iran, on February 28, the opening day of the war. The attack, according to Iranian officials, was among the deadliest single episodes since the conflict began.

Speaking to reporters, Trump dismissed evidence pointing to U.S. culpability, despite Reuters reporting that an initial internal U.S. military investigation had shown U.S. forces were likely responsible. “I have seen nothing to lead me to believe it was” a U.S. missile, Trump said. “Somebody said it was our missile, maybe it wasn’t our missile.... I don’t think it was us.” He added that because “missiles were flying all over the place” during the first day of coordinated U.S. and Israeli strikes, the truth might remain elusive.

Reuters revealed in March that the strike may have resulted from the U.S. use of outdated targeting data, a possibility that intensified international condemnation. The Pentagon has since elevated the probe but has not acknowledged any findings. U.S. officials have maintained that Washington would never deliberately target a school, which would likely be a war crime.

The strike caused global outrage. The UN human rights office called it “absolutely horrific.” Iran’s government placed the death toll at more than 175. Trump initially blamed Iran without providing evidence, then said he would await the investigation’s conclusion, while emphasising that nobody purposefully attacked the school.