PoliticsUS troops inserted by helicopter spent roughly 90 minutes on the ground near Deir al-Zour - about 80 miles from ISIS' capital in Raqqa - before witnesses say they left carrying captured ISIS fighters and bodies, according to The Washington Post, which first reported the story.
The Pentagon confirmed that a raid had taken place, but declined to offer details.
"The Coalition can confirm a US operation in the vicinity of Dayr az Zayr, Jan. 8. The U.S. and the entire counter-ISIL Coalition will continue to pursue ISIL leaders wherever they are to ensure the security and stability of the region and our homelands."
The Syrian Observatory for Human Rights said at least 25 ISIS fighters were killed during the raid, though that number has not been confirmed.
This isn't the first time US forces have conducted these types of ground raids. Though much of the focus of coalition forces has centered on retaking the Iraqi city of Mosul, the US has sent troops in to capture leaders or rescue hostages on a number of occasions.
One raid in October 2015 in Iraq's Kirkuk province freed dozens of hostages and resulted in the death of Master Sgt. Joshua Wheeler, a 39-year-old Delta Force operator who was the first American service member killed in a firefight with ISIS militants.
The military has more than 5,000 troops on the ground in Iraq currently, a number which has steadily crept up since roughly 300 troops were deployed to secure the Baghdad airport in June 2014.