The joint military-police task force investigating an alleged civilian drone deployment to North Korea has raided the spy agency and other locations. 

The joint task force said on Tuesday that it began executing search warrants at 18 locations, including the National Intelligence Service(NIS) and the Defense Intelligence Command, starting around 9 a.m. 

The task force is investigating three civilian suspects, including a graduate student surnamed Oh in his 30s, after identifying possible charges of aiding the enemy under the Criminal Act, in addition to violations of the Aviation Safety Act.

Oh told Channel A in January that he flew drones three times to verify radiation levels at a North Korean uranium facility.

Investigators are also looking into three active-duty soldiers and one NIS employee who they believe were involved.