China says it is “highly concerned” about a reported ship-to-ship transfer on the high seas that could violate UN sanctions on North Korea. Beijing is investigating the incident reported by Japan earlier this week, Foreign Ministry spokesman Geng Shuang said Thursday. Geng said China would “seriously deal” with any Chinese individuals or enterprises found to be involved. Photos of the transfer released by Japan show a North Korean-flagged tanker alongside a smaller ship that appears to be Chinese, with what appear to be hoses running between them, AP reported. Japan has reported three such incidents in the past month. China has imposed increasingly tough sanctions on North Korea over its nuclear weapons program.