Five former US officials, including a former top military lawyer, have criticised the Pentagon for not acknowledging potential American involvement in a deadly strike on an Iranian school earlier this year.
Some of those officials said it was highly unusual not to release even basic details of the strike after such a length of time.
A missile hit a primary school in Minab during the opening salvos of the US-Israeli war on February 28, killing 168 people including around 110 children according to Iranian officials.
In the two months since then the Pentagon has said only that the incident is under investigation.
US media reported in early March that US military investigators believed American forces were likely responsible for hitting the school unintentionally but had not reached a final conclusion.
Asked a series of questions by the BBC about the strike and the accusations of a lack of transparency, a Pentagon official said "this incident is currently under investigation," adding that more details would be provided when they became available.
The BBC has reviewed three historical cases in which civilians were killed during US military operations and in each case significantly more information had been released by the Pentagon within less than a month.
The current US position "strikingly departs from the standard response," said Lt Col Rachel E VanLandingham, a retired Judge Advocate General in the US Air Force and former senior legal adviser at US Central Command during the wars in Iraq and Afghanistan.
"Administrations in the past at least demonstrated fidelity, a commitment to the law of war," said VanLandingham, who argued what was "missing" from the administration's statements was a commitment to accountability and "importantly to ensure this doesn't happen again".
President Trump said on 7 March that in his "opinion" Iran was to blame for the Minab strike, without providing evidence. Days later, when asked about video showing a US Tomahawk hitting the military base next to the school, he said: "I haven't seen it" and claimed without evidence that Iran had Tomahawk missiles.
On 11 March, when asked about reports that an initial military probe had found that the US hit the school, Trump said: "I don't know about it".
Defence Secretary Pete Hegseth was asked by the BBC on 4 March about the strike and said: "All I can say is that we're investigating that. We of course never target civilian targets".
The US Department of Defense has declined to answer multiple questions about the strike. It has repeatedly declined to answer whether the Iranian military base next to the school was one of its pre-planned targets on 28 February, despite speaking publicly about pre-planned targets or operations in dozens of other instances in the war.
Last month, the BBC independently confirmed video showing a US Tomahawk missile striking the Iranian Revolutionary Guard Corps (IRGC) base next to the school. US media reports quoted unnamed military officials saying a preliminary inquiry had determined a US missile struck the school. The reports said this was due to outdated target coordinates supplied by a US intelligence agency. The Pentagon has not commented on the reports.
Wes Bryant, a former senior adviser on precision warfare and civilian harm mitigation at the Pentagon's Civilian Protection Center of Excellence, told the BBC that the military's preliminary inquiry would routinely take place to establish two things: whether the civilian harm actually took place, and whether the US was operating in the area at the time and could have caused it.
"When you meet both of those criteria, that's the only time that an investigation is actually formally initiated," he said. "From a process standpoint… that just points even more to the fact that they know already that the US caused this or else they wouldn't doing this investigation and they just don't want to acknowledge it or speak to it."
"To not even be able to have any comment on it whatsoever is just unacceptable," said Bryant, who left the Pentagon last year when staffing at the civilian harm unit was significantly reduced under Hegseth.
Another former defence official said it was common for some civilian harm investigations to take a long time depending on the complexity of the situation. "But this is a case where… it's unusually opaque in that I can tell from the situation it's actually not that complicated," the former official, who asked not to be identified due to the sensitivity of the subject matter, told the BBC.
"Normally the Pentagon would take immediate [or] relatively fast responsibility and then probably require a longer period of time to provide all the details, so to me it's problematic," the former official added.
Congressional Democrats have written several times to Hegseth asking a series of questions about the Minab strike, starting with whether the US carried it out.
The BBC has seen two of the Pentagon's response letters, sent on behalf of Hegseth, which give no answers to any of the questions. A letter sent on 2 April to Democrats said an investigating officer from outside the CENTCOM chain of command had been appointed and the results of that investigation would be shared once completed.
The BBC approached 15 Republican members of Congress asking about the administration's handling of the strike, but all declined to comment. They included top Republicans on committees covering national security in the Senate and House of Representatives.
On March 10, Republican Senator John Kennedy of Louisiana condemned the strike, telling the New York Times: "I think we made a mistake. It was a terrible, terrible mistake."
Pentagon officials have given several closed-door briefings on military operations to members of Congress since the start of the war on Iran, and have been asked questions about the Minab strike.
Adam Smith, the top Democrat on the House Armed Services Committee, told the BBC the officials said they could not comment due to their ongoing investigation, a response he called "pathetic and completely inadequate". He said there had been no admission of US responsibility in the briefings.
The BBC has reviewed three historical cases involving civilian fatalities to form a comparison with the Trump administration's response to the Minab strike.
Each of the historical cases, under both Democratic and Republican administrations, involved senior US military officials making significantly more detailed public comments than has been the case so far in the Minab strike.
Annie Shiel, a former US official who worked on civilian harm reduction at the state department, said previous cases followed a pattern where the US had "come out and said 'it was not us', only for media and [non governmental organisation] reporting to show that in fact it was a US strike, and then the US has to walk that back."
The Pentagon's appointment in the Minab case of an investigating officer outside CENTCOM was "at least on paper a good start on independence", said Shiel who is now US Advocacy Director with the Center for Civilians in Conflict (CIVIC).
But she told the BBC she would "absolutely" expect further acknowledgement of any US role while the probe is ongoing.
Corroborating details about the incident has also been complicated by the fact Iranian authorities have not granted independent access to the site. The UN Fact Finding Mission on Iran said on 17 March it had sought access but not been permitted to visit the site.
Charles O Blaha, former director of the State Department's Office of Security and Human Rights, said a lack of transparency in Washington could stem from a "reluctance" within the administration to contradict the president after he blamed Iran for the strike, a claim he described as "really far-fetched and very clearly not true".
Blaha spent 32 years in the US foreign service and is now a senior adviser to Democracy for the Arab World Now (DAWN). He attributed the relative silence in the Minab case to what he saw as a rejection by the administration of "any negative news about the war they branded as unpatriotic".
Additional reporting by Catherine Alaimo
