South Korea is conducting a probe into an unidentified drone that fell on one of its border islands during the latest cross-border exchange of artillery fire with North Korea in the western sea, military officials said Tuesday.

The drone was collected from Baengnyeong Island, just south of the western maritime border, at around 4 p.m. on Monday, shortly after the North finished its three-hour shelling drill with coastal artillery guns and multiple rocket launchers. It was not immediately known when the unmanned aerial vehicle fell on the island.

After some 100 rounds of shells dropped into waters south of the Northern Limit Line, South Korean Marines stationed on Baengnyeong Island fired about 300 shells into North Korean waters in return.

The unmanned vehicle is known to be similar to another drone that was collected from Paju, south of the demilitarized zone, on March 24, the official said, asking for anonymity as he is not authorized to speak to media.

Military and intelligence officials have dissembled the drone to identify who flew it near the border, looking into possibilities of Pyongyang's involvement.

According to another source, the collected vehicle is made of Japanese engine and Chinese components, equipped with a small camera.

"As an in-depth analysis is currently under way, we cannot confirm which country made this drone. But there is a possibility that it belongs to North Korea," the source said.

In August 2010, Pyongyang fired about 110 artillery shells near the NLL and flew a drone to conduct reconnaissance missions near border islands later in that day.

The North is believed to have developed unmanned aerial vehicles built based on China's D-4 and deployed them near front-line troops to monitor the South Korean military.

The 3.2 meter-long fixed-wing drone can fly at an altitude of 3 km with a maximum speed of 162 km per hour, capable of conducting missions within a 4-km radius. It can carry 20 kg to 25 kg of ammunition and land on ground using a parachute. (Yonhap)