Eleven U.S. service members were treated for concussion symptoms following last week's missile attack by Iran on the Al-Assad airbase in Iraq, according to multiple reports. That is in contradiction to initial reports from The Pentagon that there were no U.S. injuries.

Iran fired multiple missiles at two Iraqi bases that house U.S. forces on Jan. 8. It was a retaliation for the U.S. killing of Iranian Revolutionary Guards Gen. Qassem Soleimani earlier this month.

"While no U.S. service members were killed in the Jan. 8 Iranian attack on Al Assad Air base, several were treated for concussion symptoms from the blast and are still being assessed," according to a statement from a U.S. Central Command spokesperson obtained Thursday by Fox News and CNN.

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The service members were reportedly transported to Germany and Kuwait and will return to duty when deemed fit to do so.

Gen. Mark Milley, chairman of the Joint Chiefs of Staff, and Defense Secretary Mark Esper initially told reporters that 11 ballistic missiles inflicted moderate damage but no Americans were killed or injured.

According to CNN, a defense official explained the discrepancy by saying the concussion symptoms emerged days after the attack and that the service members were sent away for treatment as a precaution.

The Associated Press contributed to this report.