Also under scrutiny is the role of the Afghan troops who requested the airstrike after coming under hostile fire. A senior Afghan security official said the Afghan troops were a rapid-reaction commando force that had arrived in Kunduz just days before the airstrike.

The commandos, who were dispatched from Kabul on Sept. 29, the day after Kunduz fell to the Taliban, would not have been very familiar with the terrain, the official said.

Finally, investigators are interviewing the crew of the AC-130 gunship, and reviewing transcripts of the audiotapes between the aircrew and the Americans on the ground approving the strike, as well as gun-camera video of the strike itself.

But no evidence has yet emerged that the Afghan troops who called in the strike were under fire from the hospital, said the senior Afghan security official, who works closely with American forces.

The results of the first of three inquiries into the attack on the Doctors Without Borders hospital will most likely be released later this week, Pentagon officials said on Tuesday. That inquiry, conducted by NATO officers, is to determine whether civilians were killed, something that all sides quickly agreed did occur. But it may offer new insights into events leading up to the strike.

American officials now acknowledge, for instance, that the hospital was on a “protected list” of specially designated buildings like mosques or schools, to avoid the very kind of strike that happened. But investigators are still trying to determine why the Afghans, the American Special Forces and the gunship crew apparently were not aware of that.