Prosecutors launched an investigation into South Korea's arms procurement agency, suspected of forging documents and obtaining defective devices in the process of purchasing surveillance equipment, legal sources said Friday.

The Seoul Central District Prosecutors' Office said it is looking into a Defense Acquisition Program Administration's project to establish a complex surveillance system along the country's seashore, the sources said. 

The system that helps integrate existing radar and thermal imaging devices can be used in all weather conditions and aims to thwart incursions by North Korean boats that sometimes try to covertly enter South Korean waters.

The arms procurement agency has been engaged in the project since 2013 and picked a company, identified only by its initial D, as a parts supplier and contractor. The agency is expected to invest some 42 billion won into the project.

Prosecutors suspect that some parts and equipment do not meet mission requirements, and that the evaluation and verification process to designate the contractor has not been carried out in a thorough manner.

In a separate case, prosecutors have sought a formal detention warrant from a local court against a retired colonel, identified only by his surname Kim. He is suspected of forging documents and siphoning off munitions.

A series of shady deals has come to light over the last year since a special investigation team -- comprised of government, military and prosecution officials -- cracked down on corruption in the defense industry.

To continue its monitoring of unlawful activities that has been undertaken by the special team, the government opened a new department under the Seoul Central District Prosecutors' Office last month to cover corruption in the defense industry. (Yonhap)