"It's not the first time that the US deployed a drone in the South China Sea area, but it's the first time the Chinese military seized it. There must be a reason for it... It could have threatened the interests of China's islands, or China's ships and submarines. It must have been damage to Chinese interests that caused the seizure," Zhao Xiaozhuo, the director and a senior colonel at the Centre on China-America Defence Relations at the Academy of Military Science, a PLA think-tank told Hong Kong-based South China Morning Post.