US President Donald Trump has again cast doubt whether American forces were responsible for the deadly strike on a girls’ school in southern Iran, saying: “It may not have been our missile.”

Speaking to reporters on Wednesday during a meeting with NATO Secretary General Mark Rutte at the White House, Trump described the attack as “horrific”, adding that he had not seen evidence proving that the missile was American.

“There were missiles flying in every direction,” he said. “Someone said it was one of our missiles. Well, maybe it wasn’t. I haven’t seen anything that leads me to believe it was.”

The strike hit the Shajareh Tayyebeh school in Minab, in Iran’s southern Hormozgan province, on February 28, the first day of the US-Israeli attack on the Islamic Republic. Iranian authorities say 155 people were killed, including 120 children, although casualty figures have varied in international reporting.

From the outset, Tehran blamed the US military for the attack. Israel has denied any involvement.

According to a New York Times report in March, citing US officials and people familiar with the investigation, the strike was caused by a targeting error by the US military. Reuters has also reported that preliminary findings pointed to possible US responsibility, though Washington has not issued a final public conclusion.

In mid-May, the US military said the investigation, which had been assigned to an external organisation, was “complex” but “nearing completion”. A senior officer said the findings would be made public when the time was right.

Asked about the results of the investigation, Trump said: “I have to wait for it to be completed.”

He also suggested, however, that the inquiry might not produce a clear answer.

“I don’t know if they’ll ever resolve this issue, in terms of assigning blame,” he said. “I don’t know if they’ll say it was one of our missiles, because missiles were flying in all directions.”

Trump initially denied that the strike had been carried out by US forces and blamed Iran, before later saying he would “accept” the findings of the Pentagon investigation.

Agence France-Presse said it had verified that the school was located near two facilities controlled by Iran’s Islamic Revolutionary Guard Corps, the powerful military force responsible for protecting the Islamic Republic’s ruling system and overseeing parts of its regional operations. The news agency said it could not independently verify the strike assessment or the circumstances of the attack.

In late March, Volker Türk, the UN High Commissioner for Human Rights, called for the Pentagon’s investigation to be completed “as soon as possible” and for the findings to be made public.