U.S. airstrikes in Afghanistan on Aug. 22 killed some 30 civilians, far more than the military has previously acknowledged, Defense officials said Wednesday.

The probe found that the strikes against a suspected Taliban compound in the western province of Herat killed about 30 civilians — not the five to seven the U.S. originally acknowledged, according to a Pentagon official who spoke on condition of anonymity because he was not authorized to speak on the record. The New York Times first reported the new finding in its Wednesday editions.

The Afghan government and U.N. had said that the August operation killed some 90 civilians. An original U.S. investigation found that up to 35 militants and seven civilians were killed in that strikes, which strained U.S.-Afghan relations.

Gen. David McKiernan, the commander of NATO troops in Afghanistan, ordered that a second U.S. military investigation be conducted shortly after pictures and video images surfaced that appeared to show 30 to 40 victims of the attack laid out in a mosque in Azizabad, including at least 10 dead children.

A joint delegation of Afghan lawmakers and local officials investigated the aftermath of the strike and concluded that around 90 Afghan civilians, including 60 children, were killed. That finding was backed by a preliminary U.N. report.

The new U.S. report concludes that fewer than 20 militants died in the operation, the Times reported.

Zemeri Bashary, Afghanistan's Interior Ministry spokesman, said Wednesday that he had not yet seen the new U.S. report, but that the Afghan government stood by its original findings.