American special operations analysts were gathering information on the facility because they believed it was being used by a Pakistani intelligence operative to coordinate Taliban activity, the AP reports.
However, it is unclear whether the US commanders who ordered the bombing, which killed 22 patients and staff, were aware that the site was a hospital or knew about the allegations of possible enemy activity.
US intelligence materials suggested that the hospital was being used as a Taliban command and control center and may have housed heavy weapons, according to a former intelligence official familiar with the materials.
Some US analysts justified the attack by saying that the Pakistani operative, believed to have been working for his country's Inter-Service Intelligence directorate, had been killed. However, no evidence has surfaced publicly to support those conclusions about the Pakistani's connections or his demise.
The agency that ran the hospital, Doctors without Borders, has condemned the bombing as a war crime and insists that no gunmen, weapons or ammunition were in the building. It has called for an independent investigation by an international panel.
The United States has to date rejected calls for an independent probe. US officials say the two American investigations, along with an Afghan investigation, are sufficient.
On Thursday, a US tank carrying investigators from a US-Nato-Afghan team reportedly forced its way into the hospital wreckage, possibly destroying evidence in a potential war crimes investigation.
"Their unannounced and forced entry damaged property, destroyed potential evidence and caused stress and fear," Doctors Without Border said.
