"The allegations for the strike that occurred on [August] 19, is currently under formal investigation," Garver stated. "Second allegation from July 23… was determined to be not credible enough to warrant further investigation, primarily because the CJTF [Combined Joint Task Force] did not conduct any strikes in that geographic location."
In addition, US Central Command (CENTCOM) announced on July 29 that it has initiated the assessment of another strike that took place near Manbij on the same day and could have caused civilian casualties.
"This incident has been found to be credible enough to warrant a formal investigation, which is underway," Garver noted.
According to media reports, the first in the series of the strikes could have killed more than 50 people. The first incident killed 56.
"We saw a range of potential civilian casualties, anywhere from 10 to 15, up to around 73… We thought it was on the lower end of the scale," Garver said noting that the final number of casualties will be released after the investigation is concluded.
The US-led coalition of more than 60 nations has been carrying out airstrikes in Syria and Iraq since the summer of 2014.
Daesh is outlawed in the United States, Russia and numerous other countries throughout the world.