An ethnic Korean high school in Hiroshima has postponed a trip to North Korea because the controversial North Korean ferry Mangyongbong-92 canceled a port call in Niigata, school officials said Tuesday.

They said 46 seniors and five teachers at the school in Higashi Ward had planned to visit Pyongyang, Panmunjom and other places in the North from Monday to July 3.

School officials said they had wanted to let the students go, as they had been looking forward to the trip, but said future plans to reschedule were unclear because there was no telling when the Mangyongbong would make its next port call.

The ferry, which sails between Wonsan in North Korea and Niigata on an irregular basis and is suspected of involvement in illegal activities, canceled a Monday port call, citing tightened security by Japanese authorities.