A group of former researchers at South Korea's state-run arms development agency are under investigation for allegedly leaking military secrets to private firms and institutions, military authorities said Monday.“About 60 workers are believed to have left (the Agency for Defense Development) with trade secrets. The National Intelligence Service, along with its military counterpart and police, are on them to find out more,” a military official said, adding that authorities were concentrating firepower on some 20 agents suspected of glaring malfeasance.Authorities were tipped off from outside last year that retiring ranking officers at the agency often took away classified material with them. Some of those under the probe reportedly admitted to the leakage and said it was a “common practice” that retirees provide secrets to the firms or institutions that hire them.The leaked information involved the latest artificial intelligence and drone technologies as well as technologies related to cyberwarfare, according to authorities.Authorities have yet to map out how the secrets got outside and are still at work to ascertain the exact volume of the damage.“We certainly take the issue very seriously,” said an official at the agency, adding “We will come up with a foolproof plan to better protect our technologies here.”By Choi Si-young ( siyoungchoi@heraldcorp.com ).