Evidence has been piling up against the US in recent days, after President Donald Trump blamed Iran.
On Wednesday, several sources for a number of American media outlets said that outdated information probably led to the US striking the school in the city of Minab on February 28.
46 senators, the vast majority of them Democrats, are demanding answers in a letter to Secretary of War Pete Hegseth about how much analysis was done before the attack, The Hill writes.
44 of the 45 Democrats sitting in the House have signed, as have two independent members - among them former Democrat Bernie Sanders.
An investigation, which has not been released, is said to show, according to NBC News, that the United States is very likely behind the attack, but the military has not concluded that it is responsible for the incident.
The facility that was attacked belongs to Iran's Revolutionary Guard, but it also housed an elementary school for girls. Around 175 people, the vast majority of them children, were killed, according to reports that are difficult to verify so far.
The investigation that has been conducted is said to show that American missiles did not land in the wrong place, but instead struck what the US believed was a military target.
President Donald Trump, who has previously blamed Iran, said on Tuesday that he "doesn't know enough about it" to comment.
