An airstrike by the American led coalition fighting the Islamic State killed 18 Syrian fighters allied with the United States, military officials said Thursday, April 13.

The strike, which occurred Tuesday in Tabqah, Syria, was the third time in a month that the American-led airstrikes may have killed civilians and allies. As this situation was occurring, it was discovered that the pentagon had been investigating two previous airstrikes that had killed and or wounded scores of civilians in a mosque complex in Syria as well as in a building located in the west of Mosul, Iraq.

Tuesday’s strike was demanded by allies who were on the ground near Tabqah, in which the United States Central Command manages combat operations in the Middle East. The fighters had called in the airstrikes and “identified the target location as an ISIS fighting position,” by using another name for the Islamic State. The central command statement said that the target location turned out to be a “fighting position” for the Syrian Democratic Forces, who have been fighting the Islamic State alongside the United States. It was unclear whether the strike came from an American warplane or one from the other coalition partners.

“The coalition’s deepest condolences go out to the members of the S.D.F and their families,” said the Central Command center in a statement. “Tragic.”

As the American-led military campaigns against the Islamic State, Military officials say Iraqi forces will retake Mosul in what is to be seen as the last big urban hurdle to defeating the extremist Sunni militant group in Iraq while forces allied with the United States are moving in on the group’s de facto capital of Raqqa, in Syria.

President Trump himself has indicated that unlike President Barack Obama, who had his white house scrutinize many military operations, he will leave more operational decision making to the Pentagon as well as the American commanders in the field.