The Defence Ministry's Criminal Investigation Command raided the cyber warfare unit Tuesday as the ministry expanded its probe into allegations that some unit members posted political comments online during last year's presidential election.
In an interim report after a week of inquiry into the case, the ministry confirmed that three civilian employees and one non-commissioned military officer registered "private" comments on their blogs and Twitter.
Based on their statements, the four employees were not directed by higher authorities to make the online postings, officials said.
The ministry turned a fact-finding survey into a full-scale investigation to see if the employees violated the military criminal law and ministry regulations that mandate service members maintain political neutrality.
"We have so far confirmed four social networking service accounts, which were reported in the media. The four (members of the command) admitted that they were their accounts," ministry spokesperson Kim Min-seok told reporters.
"To ensure that there would be no suspicions left at all about the case, we will exhaustively investigate."
The survey began last Tuesday after some opposition lawmakers and media raised suspicions that the cyber command might have mobilized some of its members to post election-related comments online to help then-candidate Park Geun-hye.
The suspicions came amid persisting bickering over the allegations that former National Intelligence Service chief Won Sei-hoon directed his operatives to post political comments online to help tip the scale in favour of Park.
During the expanded probe, ministry officials and civilian cyber experts will investigate whether there are additional suspects and if the suspects made political postings with directives from higher authorities.