KABUL, Afghanistan — The top American commander in Afghanistan, Gen. John F. Campbell, said Wednesday that several service members had been suspended from duty after an internal military investigation of the American airstrike on a Doctors Without Borders hospital in Kunduz last month.

Calling the airstrike a “tragic mistake,” General Campbell read a statement announcing the findings of the investigation, which he said concluded that “avoidable human error” was to blame, compounded by technical, mechanical and procedural failures. He said another contributing factor was that the Special Forces members in Kunduz had been fighting continuously for days and were fatigued.

The strike, which involved repeated attacks by a Special Operations AC-130 gunship early on Oct. 3, killed 30 people, mostly patients and Doctors Without Borders staff members, and gutted the main hospital building. The aid group said the attack continued for more than an hour despite repeated calls to the military by staff members, and despite the hospital’s coordinates having been repeatedly sent to the American command.

General Campbell and his staff did not say how many people were being disciplined, or how. But a senior United States military official, speaking on the condition of anonymity, said one of those punished was the Army Special Forces commander on the ground in Kunduz during the fighting. The official would not identify the commander by name but said the officer, a captain, was relieved of his command in Afghanistan on Wednesday morning.