(CNN) The US-backed Syrian Democratic Forces (SDF) captured two Americans in Syria who are suspected of being ISIS fighters, the militia said in a press release Sunday.

The militia identified the men as Warren Christopher Clark (Abu Mohammad al-Ameriki) and Zaid Abed al-Hamid (Abu Zaid al-Ameriki).

The SDF said Clark is originally from Houston, but it gave no specific location in the United States for the other man's origin.

The Americans were captured in a group that also contained fighters from Ireland and Pakistan, SDF said.

A Pentagon spokesman said the incident is under investigation.

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