Story highlights The drone had 10 aerial photographs of the Terminal High Altitude Area Defense system

The US-built missile defense system is being deployed in South Korea

Seoul, South Korea (CNN) South Korea said it has recovered a crashed North Korean drone that was spying on a controversial US-built missile system that is being deployed in the country.

The unmanned aerial vehicle, which was discovered Friday, was equipped with a SONY digital camera that had hundreds of photographs on it, some from 2-3 kilometers (1.2-1.8 miles) high, according to an official with the South Korean military.

About 10 of them were aerial shots of the Terminal High Altitude Area Defense (THAAD) system -- more than 100 miles away from the border -- which is designed to shoot North Korea's ballistic missiles down before they can do damage, the official said.

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It likely crashed after running out of fuel, the official added.

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