KABUL — A series of errors, human and technical, led to an American gunship bombing a Doctors Without Borders hospital in the northern Afghan city of Kunduz last month, killing 30, a U.S. military probe has concluded.

Several American personnel, most likely pilots and U.S. special operations soldiers, who made the decision that led to one of the deadliest incidents of civilian casualties of the war, have been suspended and could face further disciplinary action, senior U.S. officials told reporters in Kabul on Wednesday.

“This was a tragic and avoidable accident caused primarily by human error,” said Gen. John Campbell, the top U.S. commander for Afghanistan, adding that it was “compounded by systems and procedural failures.”

The medical facility, the location of which was widely known in Kunduz, was misidentified as a target by the American personnel, Campbell said. They thought they were striking the headquarters of the Afghan intelligence service several hundred meters away, which the Taliban had reportedly seized.

Investigators also concluded that those who requested the air strike, as well as those who executed it from the air, did not take the proper measures to verify that it was a legitimate military target, Campbell said.

But many questions remained after Campbell presented the findings. Just before the attack on the hospital, a U.S. air strike pummeled an empty warehouse across the street from the Afghan intelligence headquarters. How U.S. personnel could have confused its location only a few hours later is not clear, nor is it clear why the gunship repeatedly bombed the hospital when there was no return fire.

According to the report’s findings, on the night of Oct. 2, Afghan special forces requested air support to help clear the Taliban from the headquarters of the intelligence service, known as the National Directorate of Security, or NDS. The U.S. Special Operations commander on the ground agreed, but he had no clear view of either the NDS building or the Doctors Without Borders hospital.

From this point on, the errors began, said Campbell.

The powerful AC-130 gunship dispatched to provide air support flew out quickly without conducting a normal mission brief and without vital information, including a list of no-strike areas, which would have included the hospital. And during the flight the electronic systems malfunctioned, preventing the pilots from sending or receiving emails or electronic messages or transmitting video back to control rooms, Campbell said.

In addition, the aircrew thought the aircraft was targeted by a missile, which forced the gunship to move away from its original flight path, lessening the accuracy of some of its targeting systems, Campbell said. By the time the plane got the strike coordinates for the NDS building, they correlated to an open field about 330 yards away from the NDS building . So the aircrew decided to visually target the hospital, which was near the field and superficially matched the description of the NDS compound.