The US military is looking into whether an American service member was involved in carrying out an April 7 attack on the Green Village base in eastern Syria that left four Americans wounded.
A service member from the U.S. is currently in the U.S. and could be a suspect in the bomb attack.
The Army and Air Force are still investigating the attack, which may or may not lead to a conviction in a court of law, according to the spokesman.
The U.S.-led anti-Islamic State coalition said that investigators initially thought the attack came from outside the base, as is typical for mortar and rocket attacks in the region.
Military officials told CNN that the attack was carried out with a bomb that was more powerful than a grenade.
Security footage showed a figure moving quickly in two instances around the time of the attack, but it wasn't clear if it was the same person in both cases.
The four service members who were wounded returned to duty after being treated for their injuries.
There is no clear reason behind the Green Village attack.
In 2015, a group of people came together to fight the Islamic State in Iraq and Syria. More than 900 U.S. troops are still in Syria to support the Kurds in their fight against the Islamic State. The Green Village attack was blamed on Iran-backed militias in Syria. Iran has been accused of supporting militias in Iraq and Syria that have carried out attacks on the US.
Four U.S. personnel were injured in a bombing in Syria.