The government said three unmanned aerial vehicles (UAV) that crashed in South Korea were definitely sent by North Korea to spy over frontline military units and the Blue House.

A Seoul-Washington joint investigation team concluded that the departure and intended return points of the three drones found in Paju, Baengnyeong Island and Samcheok were North Korean territory, the Ministry of National Defense announced yesterday at a briefing.

Based on an analysis of a memory chip and the memory sticks of digital cameras in the drones, the investigators were able to piece together their flight plans. The plane found on March 30 on Baengnyeong Island was sent from an unidentified location 27 kilometers (16.7 miles) away from Haeju, a western coastal city in North Korea near the border. It was supposed to return to the same point.

According to the photos taken by the digital camera inside, the drone was found to have completed most of its 50-minute flight program, the ministry said. The plan was to hover over several military units near Socheong Island and Daecheong Island in an S-shaped route.

The drone discovered on March 24 in Paju, a western border city, was sent from 5 kilometers northwest of Kaesong in North Korea and ordered to return to the same point. It also accomplished most of its programmed route, the ministry said.

The latest one, found on April 6 in Samcheok, an eastern coastal city, was launched 17 kilometers east of Pyonggang County, Kangwon Province, North Korea, and was also ordered to return to the same point.

It was programmed to fly over several military facilities, the ministry said, but investigators could not confirm its actual flight plan. The South Korean man who discovered the drone and reported it to the military said he deleted all files from the digital camera’s memory stick that he found inside and intended to use it himself.

The ministry said officials were still analyzing the departure points to pin down whether they had military units or airfields.

The small drones could have been sent from a mobile launch pad, according to the ministry.

Discussing allegations published online that the drones appeared to be made by a Chinese manufacturer, a ministry official said, “The shape and other characteristics of the drones were very similar to Chinese drones, as alleged by netizens. We asked the Chinese Embassy in Seoul to offer some materials about the alleged Chinese products, but we haven’t received any answers.”

The drone in Paju flew lower than its planned altitude, the ministry said, possibly due to a faulty engine. The planes on Baengnyeong Island and in Samcheok crashed because they ran out of fuel, the ministry said.

When asked about the maximum flight distance for a round trip for one of the drones, the official said it would be between 200 kilometers and 420 kilometers, based on similar Chinese products. The drones could carry three or four kilograms of chemical weapons or a bomb, the official said.

“We analyzed how much the drones could carry only loaded with fuel and without a digital camera,” the official said. “The result was that they could carry three or four kilograms each, which means it could effect people within 10 or 20 meters of its radius” after it landed with a payload.

BY KIM HEE-JIN [heejin@joongang.co.kr]