American forces were not under direct fire when local Afghan forces asked for air support just prior to the U.S. bombardment of an Afghan hospital that killed at least 22 people, the coalition's top commander in Afghanistan said Monday.

The Pentagon had previously said U.S. troops were under direct fire.

"I've ordered a thorough investigation into this tragic incident and the investigation is ongoing," U.S. Army Gen. John Campbell said. "The Afghans ordered the same. If errors were committed we'll acknowledge them. We'll hold those responsible accountable and we will take steps to ensure mistakes are not repeated."

Related: Doctors Without Borders Hospital in Kunduz Hit by Apparent U.S. Strike

Campbell said that Afghan troops were under direct fire and "called in for fire to support them." He acknowledged that initial statements from the coalition indicated that U.S. Special Forces were under direct fire, but that was not the case and he is "correcting that statement here."

He said that U.S. Special Forces were in the area, just not under direct fire.

Campbell declined to answer whether the rules of engagement allow for the Afghans to call in American airstrikes and what kind of fall back or fail-safe system is in place.

Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

He had been previously scheduled to appear before the Senate Armed Services committee on Tuesday to brief lawmakers on the state of military efforts in Afghanistan. Questions will now likely include the airstrike on the hospital.

Military officials told NBC News over the weekend that Afghans cannot call in airstrikes — that they do not have the training. However, they can report to the U.S. and coalition that they are under fire from a location and the U.S. or coalition partners there can call it in. Officials said the U.S. would not strike without target verification first.

It isn’t clear how the Afghans asked for air support, but Campbell seemed to suggest both of those policies were violated.

A preliminary report into the bombing should be ready “in the next couple of days,” he added.

The White House confirmed on Monday that, in addition to the Department of Defense investigative process that is already underway, there also will be an investigation that is conducted by NATO and a third joint investigation carried out by U.S. military personnel alongside Afghan security officials.

"The president obviously has confidence in these three investigations to provide that full accounting that he seeks, and his expectation is that details won't be whitewashed, they'll be a full accounting of what exactly transpired, so that if it's necessary to take steps to prevent something like this from ever happening again, that those reforms are implemented promptly and effectively," White House press secretary Josh Earnest told reporters on Monday.

Related: Doctors Without Borders Hospital Bombing: Witnesses Recount Strikes

Twelve Doctors Without Borders staff along with seven patients, including three children, were killed after the airstrike hit the international charity's hospital in the Afghan city of Kunduz.

Another 37 others were injured in the strike: 19 staff members, including five in critical condition, and 18 patients and caretakers, according to Jason Cone, the executive director for Doctors Without Borders in the U.S. The organization, which said it reached out to U.S. and coalition forces to inform them during the attack, didn't comment on the identities of the victims, but said all international staffers were alive and accounted for.

The organization condemned the airstrike, which they said had "no justification" and have requested "an independent, fully transparent investigation" into the matter.

"The U.S. military has admitted that the airstrike was their fire, but what is changing is the description of events since this weekend. So, it started with a tragic incident, to collateral damage, and now what we hear it was a U.S. strike but on request, under the responsibility of the Afghan government," Meinie Nicolai, the organization's president told NBC News. "The reality is they dropped the bombs and they hit a fully functioning hospital at the front line doing a humanitarian duty. So, the responsibility is pushed off, the U.S. military remains responsible for the targets they hit, even if you're part of a coalition."

Doctors Without Borders said it had treated 394 people who had been injured since fighting began a week ago when Taliban militants conquered the provincial capital in a stunning setback for the Western-backed government. It was the first major urban area to fall to the Taliban since the U.S.-led invasion of Afghanistan in 2001.

Interior Ministry spokesman Sediq Sediqqi told NBC News that up to 15 militants had "taken position inside the hospital compound" and begun firing on Afghan forces.

"There was an operation conducted to eliminate the threat. The hospital has been damaged and there are some casualties," Sediqqi added. "All of the terrorists were killed, but we also lost doctors."