Two members of Operation Inherent Resolve were killed and another five were wounded by an improvised explosive device in Syria on Thursday.

A U.S. defense official confirmed to Military Times that one of the service members killed was an American. The attack took place in the "vicinity of" Manbij, the official said. It was not immediately clear if the IED hit a vehicle or if the forces were on foot patrol.

The official spoke on the condition of anonymity and did not give the nationality of the other individual who was killed.

“Wounded personnel received immediate care and are being evacuated for further medical treatment,” according to a statement from U.S. Central Command.

The names of the deceased and wounded have not yet been released.

Manbij is a mixed Arab and Kurdish town near the border with Turkey. Coalition forces have been in the area since around August 2016, when they supported locals in the liberation of the area from the Islamic State.

“We have maintained a relationship with the Manbij Military Council (MMC), which was created to defend Manbij from [ISIS],” an OIR official previously told Military Times.

It is not immediately clear who placed the IED.

In January, Turkey began a military offensive over its border into the Syrian city of Afrin in order to eliminate Kurdish fighters it considers terrorists. The Turkish government has previously threatened to extend that operation to Manbij, despite the presence of U.S. forces there.

Details pertaining to the incident are being withheld pending further investigation, the CENTCOM statement added.