TOKYO — A boat carrying four crew members sank Thursday while being towed by a North Korean cargo ship off Japan’s northwestern coast, leaving one person missing after the Japan Coast Guard rescued three, officials said.

North Korea’s Rescue Coordination Center notified the Japan Coast Guard’s regional headquarters in Kyoto earlier Thursday that four crew members had fallen overboard about 104 kilometers (64 miles) southwest of one of the Oki islands called Nishinoshima.

The area where the incident occurred is inside Japan’s exclusive economic zone.

The Japan Coast Guard told The Associated Press that officials were investigating the crew members’ nationalities and whether their sunken boat was connected to the North Korean cargo “Kum Ya.”

The coast guard was also investigating what the boat had been doing in the area.

The Japan Coast Guard said it dispatched patrol vessels and aircraft for the search and rescue operations and plucked three crew members. Two of them were conscious but a third one was presumed dead, the coast guard said.