The South Korean military opened an investigation into the indigenously developed military helicopter Surion after some of the fleet had cracked windshields and other cracking problems, the defense procurement agency said Monday.

"Some of the (locally operational) 40 or so Surions have shown problems on their airframes," Kim Si-cheol, spokesman at the Defense Acquisition Program Administration (DAPA), said in a press briefing earlier in the day.

Currently, the DAPA is consulting the chopper's producer, Korea Aerospace Industries Ltd. and other defense procurement bodies on how to resolve the issue, Kim said.

According to DAPA officials, the investigation has shown so far that four Surion choppers had cracks developed in the vibration absorption devices in the left part of their airframes and some other choppers had cracked windshields.

The defects, however, have yet to result in any safety problems with the Surion fleet, the officials said.

The military will continue to allow their flights until they can come up with countermeasures next month, according to the DAPA.

The measures may include a windshield upgrade to affix protection films, the officials added.

Surion was produced in a 1.3 trillion won (US$1.1 billion) military procurement project to build South Korea's first-ever indigenous helicopter. Since the first flight test in 2010, the chopper has been adapted to non-military missions such as forest preservation, police and medical transport. (Yonhap)