WASHINGTON — Senior U.S. military officials are in the final stages of reviewing an internal investigation into a deadly airstrike on an Iranian elementary school and preparing to share it with lawmakers, according to a person familiar with the probe.

But there is growing concern in Congress and the Pentagon that the Trump administration will classify and shield its results from the public, four congressional officials and the person familiar with the investigation said.

U.S. Central Command, which was leading the investigation, has completed it, according to the person familiar with the probe. Lawmakers with oversight over the Pentagon have not received any details of its results or a timeline on when they might, this person said.

Asked about the strike Wednesday, specifically whether he would hold anyone in his administration accountable for it, President Donald Trump said, “mistakes are made, war is nasty.” He said that the strike remains under investigation and that while a report could be released as early as Thursday, reporters should ask Defense Secretary Pete Hegseth who is overseeing the process.

A Pentagon spokesperson said the matter is still under investigation.

Marking the investigation classified would greatly curtail access to how the deadliest attack on civilians during the U.S. and Israeli war with Iran happened. The strike on the Shajareh Tayyebeh elementary school in Minab occurred on the first day of the war, killing more than 170 people, most of them children.

The U.S. military had been targeting the area near the school Feb. 28, and preliminary findings showed that a U.S. munition was likely responsible for the strike, NBC News has reported, citing an American official and a person familiar with the preliminary findings.

The length of time it has taken the military to complete the investigation — nearly four months — as well as difficulties lawmakers have said they’ve had obtaining information about the war from the Pentagon have fueled concerns the administration could attempt to avoid disclosing the results.

“Our concern is that Hegseth will classify the report and prevent it from being released,” the person familiar with the investigation said.

Democratic Sen. Mark Kelly of Arizona, who sits on both the Intelligence and Armed Services committees, told NBC News, “Of course they are going to try to classify the report.”

Another Democratic senator said, “I’d be shocked speechless if they didn’t say it was classified.”

Classifying the investigation into the strike would appear at odds with the Pentagon’s vow to be transparent about its findings.

CENTCOM’s commander, Adm. Bradley Cooper, told lawmakers last month during sworn testimony that as soon as the investigation is complete, “I’m fully committed to transparency.”

“It’s a complex investigation,” Cooper said. He said at the time that it was near completion.

In past accidental attacks on civilians during military operations, the Pentagon has publicly disclosed its role, including a special forces raid in Yemen and a bombing in Iraq that killed more than 100 civilians, both during the first Trump administration; an attack on an Afghan hospital during the Obama administration in which at least 42 people were killed; and a drone attack in Afghanistan during the George W. Bush administration that killed 10 civilians.

The preliminary findings of the Minab investigation had found that outdated intelligence likely led to the strike, NBC has reported, citing a U.S. official and three sources familiar with the preliminary findings.

A video that was geolocated by NBC News also showed what appeared to be an American Tomahawk missile, according to experts, hitting a compound belonging to Iran’s Islamic Revolutionary Guard Corps next to the elementary school.

“We have known for some time that a Tomahawk missile hit that school; it was on video,” another Democratic senator said, adding that if the administration marks the investigation into the strike classified, it would be “trying to shield itself from having to admit it to the public.”

Trump said at one point, without evidence, that Iran or “other countries” could be responsible.

“In my opinion, based on what I’ve seen, that was done by Iran,” he told reporters less than two weeks after the strike. But the results are expected to show the U.S. was responsible for the strike, based on the initial findings.

Lawmakers have for months pressed the Pentagon for details of the strike, including in a March letter to Hegseth from 120 Democrats.

Among their questions was what role AI may have played in selecting targets in Iran, something that could be addressed in the results of the Pentagon investigation.

“If artificial intelligence is used, is it subject to human review and at what point? Was artificial intelligence, including the use of Maven Smart System, used to identify the Shajareh Tayyebeh school as a target? If so, did a human verify the accuracy of this target?” the lawmakers asked in the March letter.