North Korean and Chinese security forces have reportedly formed joint teams to clamp down on North Korean defectors.

Japan’s Asahi Shimbun says that for the operation, the North has sent some 100 members of their secret police to China and that China has also mobilized hundreds of armed agents.

The members of the North Korean secret police are known to have been sent to areas where defections often occur, such as the northeastern regions of China and the provinces of Yunnan and Guangxi, both of which are considered gateways to Southeast Asia.

Asahi says that the joint operation began in early June and that dozens of escapees have already been caught and sent back to North Korea.