One of the four sent their company a text message that said , `` Help me '' The four are being investigated for entering a military zone without authorization . They also may have videotaped military targets , Chinese state media says . The arrests come amid the two nations ' diplomatic battle over Japan 's detainment of a Chinese fishing captain . China has been conducting air and sea patrols in the South China Sea since 2012, when it began building artificial islands on reefs there.
One of the four sent their company a text message that said , `` Help me '' The four are being investigated for entering a military zone without authorization . They also may have videotaped military targets , Chinese state media says . China has been conducting air and sea patrols in the South China Sea since 2012, when it began building artificial islands on reefs there.