"The combined international and Afghan force was initially fired upon by unidentified forces, then believed not to be Pakistani military, and legitimately responded in self-defense," NATO said in a statement soon after the US Department of Defense issued a similar investigation note at the conclusion of their probe into the incident.
"The investigation has ascertained that a series of mistakes were made on both sides in failing to properly co-ordinate their locations and actions, both before the operation and during the resulting engagement," NATO said.
However, neither of the statements clarified whether they were talking about separate investigations or the same.
"The combined force did not knowingly fire at the Pakistani forces. The investigation has substantiated that close air support was employed in self-defense in response to intense, heavy machine gun and mortar fire initiated by what turned out to be Pakistan forces near the border in the vicinity of Salala," NATO said.
The US-led military grouping said a thorough review of the operational plan and communications during the incident substantiate the conclusion that the Pakistani forces were not knowingly targeted and the action of its forces was legitimate within the Laws of Armed Conflict and within their Rules of Engagement.
"Immediate steps have been taken to reduce the risk of similar incidents in the future. ISAF is also reviewing the manning, training, and certification of the Border Coordination Centres to assist in this effort," it said.
The NATO chain of command extends their sincerest, heartfelt condolences to the families of those Pakistani Security Force members who were killed or injured in this incident, the statement said.
The Department of Defense had also expressed its regret.
Meanwhile, the Wall Street Journal in its lead report said that the US erred in deadly attack.
"The US is poised to concede for the first time that it bears significant responsibility for last month's American air strike that killed 24 Pakistani troops, US officials said, an admission that is expected to embarrass the American military but points to a way out of the deepening mistrust between the two countries," the Journal said.
According to the daily, the military investigation found that US and Afghan commandos incorrectly concluded there were no Pakistani forces in the Afghan border area where the coalition was conducting an operation on November 26.
That assessment cleared the way for an air strike that devastated Pakistani positions, it said.
"After the initial strike, the US compounded its mistake by providing inaccurate data to a Pakistani military representative at a border-coordination center, missing an opportunity to stop the fighting, these people said," the daily reported.
The WSJ said the new report's conclusions uphold key portions of Pakistan's version of events.
It also conflicts with some early US accounts, which said Pakistanis gave an all-clear that opened the way for the most deadly friendly-fire incident of the 10-year Afghanistan war.
The NATO attack had triggered an angry reaction in Pakistan and the government closed all NATO supply routes and forced the US to vacate Shamsi airbase in Balochistan province, which was reportedly used by CIA-operated drones.
Pakistan has now sought "new terms of engagement" with US that guarantees the country's sovereignty and ensures that there is no unilateral action like the raid that killed Osama bin Laden.