Rescuers are searching for seven Koreans who disappeared after a helicopter crashed Friday while taking off from a set of South Korea-held islets claimed by Japan, officials in Seoul said.

The helicopter had just picked up an injured fisherman from Dokdo, known as Takeshima in Japan, when it went down on Thursday night about 600 meters south of the islets with seven people on board, a Korea Coast Guard representative told reporters.

The missing were described as five rescuers, a civilian and the fisherman.

The representative said he was unable to confirm whether any remains had been found but said the chopper was found about 72 meters (240 feet) below the surface and was “not in its original shape.”

In addition to the coast guard, the South Korean National Fire Agency and civilian boats were searching for the missing, and the defense ministry sent planes and divers to the area, a South Korean fire agency spokesman said.

The chopper was a Eurocopter EC225 made by Airbus.

“The patient was on a fishing boat when he lost one of his fingers through an accident, and the crew took him to Dokdo and waited for the rescue helicopter there,” the fire agency official said.

“The patient needed an immediate medical operation that could have only been done at facilities on the mainland,” he said.

Seoul has controlled the islets in the Sea of Japan, which it calls the East Sea, since 1945, when Tokyo’s brutal colonial rule of the peninsula ended. Japan still claims sovereignty over them.