Figures presumed to be serial numbers have been found on the fuselage of all three drones that crashed in South Korea recently.
The Defense Ministry on Monday said the number 24 was painted on the body of the unmanned aerial vehicle that crashed in Paju, Gyeonggi Province on March 24 and the number 6 on the drone that crashed on Baeknyeong Island in the West Sea on March 31. The drone discovered in Samcheok, Gangwon Province on Oct. 4 last year bore the number 35.
All look as though they were written with marker pens.
"We need to investigate further what exactly the numbers mean," ministry spokesman Kim Min-seok said. "We've found handwritten numbers on fragments of all North Korean weapons that have recently been found."
The handwritten Arabic No. 1 was found on the fragment of a 122 mm multiple rocket launcher shell during the shelling of Yeonpyeong Island from North Korea on Nov. 23, 2010.
The marker "No. 1" handwritten with a blue marker pen was found on the propeller of the torpedo that hit the Navy corvette Cheonan on March 26, 2010.
A North Korean light torpedo salvaged from South Korean waters in 2003 also bore the Arabic No. 4 on it.
Experts believe the numbers are serial numbers. All of the three drones are believed to have been produced from molding presses, which means they can be mass-produced. If so, this suggests that the North has produced more than 65 such small drones.
Markers with Roman-Arabic numerals, "III-1," "III-2," and "III-3," were found on the three batteries of the Samcheok drone. The batteries also had a tag indicating that they first started in use on June 25, 2013.
The Samcheok and Paju drones are almost the same shape and make, but the Paju drone is believed to be a newer model.
"We presume that the Samcheok drone crashed due to lack of fuel," Kim added.