The US military was warned by the CIA of the presence of civilians, including children, seconds before the drone strike hit Kabul, CNN reported on Saturday.
Three anonymous sources told CNN the alert was sent out after the strike was launched, though it's unclear when exactly the CIA's warning was issued.
The August 29 drone strike, which the Pentagon said targeted an Islamic State suicide bomber, killed 10 Afghan civilians including seven children.
However, a New York Post investigation from earlier in September found that who the US military reportedly believed was a suicide bomber with explosives in his Toyota Corolla, turned out to be an aid worker returning to his family.
US Secretary of Defense Lloyd Austin identified the man killed in the drone strike as Zemari Ahmadi, a 14-year employee of Nutrition and Education International, a US NGO that fights malnutrition.
"We now know that there was no connection between Mr. Ahmadi and ISIS-Khorasan, that his activities on that day were completely harmless and not at all related to the imminent threat we believed we faced," Austin said in the statement.
On Friday, the head of the US Central Command Marine Corps General Frank McKenzie called the strike a "tragic mistake."
The drone strike came three days after an Islamic State suicide bomber killed 13 US troops and dozens of Afghan civilians.
Reuters contributed to this report.