Search operation under way after 11 member-strong Keoyoung Sun turns over off southwestern Japan’s Honshu main island.

Seven people have been pronounced dead and two are still missing after a South Korean-flagged tanker capsized off Japan in rough seas, according to officials.

The Keoyoung Sun with 11 crew members turned over on Wednesday near Mutsure Island, just off southwestern Japan’s Honshu main island, about 1,000km (620 miles) from the capital, Tokyo.

The coastguard initially said it had rescued nine people out of an 11-member crew made up of two South Koreans, including the captain, eight Indonesians and a Chinese national. It later said one, an Indonesian national, was still alive.

Another person found was in unknown condition, officials said. Earlier, authorities said all nine found were in “unknown condition.”

A rescue operation for the remaining two people missing is still under way.

The ship was en route from the Japanese port of Himeji to Ulsan in South Korea from, according to NHK.

There was no immediate information on what caused the ship to capsize.

The crew had alerted the coastguard that the tanker was tilting as it took refuge near Mutsure Island due to rough weather, according to Japanese broadcaster NHK.

The tanker was carrying 980 tons of acrylic acid, officials said. No leak has been detected, and officials are studying what environmental protection measures may be needed in case there is a leak.

Footage from NHK showed the overturned red hull of the ship as well as a life raft, as a coastguard ship pounded through heavy waves and a helicopter flew overhead.

The ship completely capsized by the time rescuers arrived at the scene, the coastguard said.

According to the specialist website vesselfinder.com, the Keoyoung Sun is a chemical and oil products tanker built in 1996, measuring 69 metres (226 feet) in length.

There was no immediate comment by the ship’s operator.