The Navy has retrieved the debris of North Korea's long-range rocket launched earlier this week and a joint investigation team will analyze it to get a glimpse of the communist state's rocket technology, the defense ministry here said Friday.

Less than two hours after Wednesday's liftoff, a South Korean Aegis destroyer deployed in the Yellow Sea discovered an object, believed to be part of a fuel container from the first stage of the rocket, near the trajectory announced by the North.

"The Navy's Deep Submergence Rescue Vehicle retrieved the debris of the rocket's first stage at 00:26 a.m. and was delivering it to the Second Command Fleet in Pyeongtaek," west of Seoul, a ministry official said.

The first stage of the North's Unha-3 rocket fell in the sea off the Korean Peninsula, while the second landed east of the Philippines.

After the Navy first discovered the object on the launch day in waters about 160 kilometers west of Gunsan in Jeolla Province and about 430 km south of the North's launch site, a rigid inflatable boat (RIB) attached a dragline to the debris.

The object started to submerge at around 4 p.m. on that day at a depth around 80 meters.

The salvage operation started at 4 p.m. Thursday and succeeded in retrieving the 7.6-meter-long, 2.4-diameter object, which is inscribed with the word "Unha," the rocket's name, after eight hours of work, the ministry said.

The chunk of debris is expected to arrive at the Pyeongtaek port at about 11 a.m. for further analysis by military officials and rocket scientists, the ministry said.

"It is expected to become a useful material for analysis of North Korean rocket's technology," ministry spokesman Kim Min-seok said.

As soon as the debris is delivered, a joint investigation team composed of officials from the defense ministry, the Joint Chiefs of Staff and the Agency for Defense Development as well as civilian rocket scientists will examine the rocket debris, a senior ministry official said.

American experts, who have expertise in analyzing missiles developed by the Soviet Union and Iran, will also participate in the investigation, the official said.

The North is known to have used solid fuel for its rockets, but its specific materials have not been unveiled to the outside world.

As the rocket engine is fitted with four booster engines of Nodong-B ballistic missile, the analysis would provide knowledge of the shorter-range missile launched from Musudan-ri in its northeast in April 2009, experts say.

When Pyongyang's last attempt in April ended in failure after the rocket flamed out shortly after liftoff, it was smashed into about 20 pieces.

Although North Korea claims the launch was meant to send a satellite into space, South Korea, U.S. and other nations consider it as a covert test for ballistic missile technology banned by the United Nations for its past missile and nuclear tests. (Yonhap News)