A US Air Force technical sergeant has been charged in connection with an attack in April at a US military base in northern Syria that injured four US service members, according to an Air Force statement.

Sgt. David D. Dezwaan Jr., an explosive ordnance disposal expert assigned to the 75th Air Base Wing, Hill Air Force Base, has been charged by the Air Force, under the Uniform Code of Military Justice, with aggravated assault; dereliction of duty; destroying military property; reckless endangerment; accessing a government computer with an unauthorized purpose and obtaining classified information.

CNN first reported in June that the US military was investigating whether an American service member set off explosives in an insider attack on the small US base in northern Syria

The charges are brought after a criminal investigation into the incident that took place in Green Village, Syria. Two sets of explosives were set off on the base. An investigation by the Army's Criminal Investigation Division and the Air Force Office of Special Investigations led to Dezwaan being arrested in June.

A preliminary hearing is due to take place at Hill Air Force Base on August 23. The Air Force said in its statement that anyone facing charges is “presumed innocent unless and until proven guility.”

Initially, US officials said they believed the April 7 attack was caused by indirect fire on the base in a similar manner to rocket and mortar attacks that have been carried out in the region by militia groups. However, a week later, a military statement said that after “further investigation” the attack was believed to a result of “deliberate placement of explosive charges by an unidentified individual(s) at an ammunition holding area and shower facility.”

The explosives used were described to CNN by two officials as “not insignificant” with more detonation power than a hand grenade. One official characterized the explosives as “military grade.”

The four injured service members were diagnosed and treated for traumatic brain injuries after the explosions but returned to duty later in April.

After the incident, a “commander's investigation” was initiated by the US Central Command, which oversees operations in Syria, but it was turned over to the Criminal Investigation Division when it became clear the explosive pattern was not caused by incoming fire, officials say.

The Biden administration maintains around 900 troops in Syria, including special operations forces to advise and assist Syrian Democratic Forces.