"We are very sorry for causing such a terrible accident," Yasuo Matsunaga, director of the Port and Airport Department of the Kanto Regional Development Bureau, said at a press conference held in Yokohama on Sunday afternoon.
The accident occurred during construction work to maintain Japan's southernmost islands. Five workers were killed and two others went missing Sunday morning at the pier construction site at the Okinotorishima islets, located 1,700 kilometers south of Tokyo.
Due to the island's remoteness, rescue efforts proceeded with great difficulty, leaving officials at the Land, Infrastructure, Transport and Tourism Ministry, which ordered the construction work, and those at companies involved struggling to collect information.
According to bureau officials, a metal pier that was set afloat on the sea started to tilt immediately after two boats began hauling it toward the site where the pier was to be installed about 500 meters away.
Sixteen workers on the pier were thrown into the ocean. All were wearing life jackets, but only nine were rescued right away. Five were eventually found dead, and two others were missing.
Rules at the construction site call for work to be suspended when waves reach more than 1.5 meters high and the wind speed is greater than 10 meters per second. However, the weather conditions were relatively calm at the time of the accident.
"When the pier was set afloat on the sea, there were no problems at that point," Matsunaga said. "However, it started tilting as it was being pulled, and in a matter of minutes, the pier overturned." The details of the accident are still unknown, he said. "All I can possibly say is that some kind of trouble occurred as the pier was being pulled."