A 998-tonne oil tanker was listing off the Japanese coast on Thursday after an explosion and subsequent fire that sent towering columns of acrid smoke into the sky.
One person was still unaccounted for more than two hours after the accident.
The tanker had unloaded its cargo of crude oil and was stationary close to the coast of Hyogo prefecture, around 450km west of Tokyo, when the explosion happened.
Akihiro Komura, an official from Syoho Shipping, a Hiroshima-based shipping firm that owns the vessel, said that seven of the eight Japanese crew were accounted for, but the fate of the captain was not yet known.
“The ship unloaded crude oil at a port in Hyogo prefecture, and the tanker was virtually empty when the accident occurred,” he said.
“I heard that a crew member was using a grinder to remove paint and that seems to have triggered the blast, which we believe could have occurred when the remnants of the oil caught fire.
“It is a Japanese ship and belongs to our company. All the crew members are Japanese nationals. We have confirmed seven out of the eight are alive and one, believed to be the captain, is still missing.”
News of the incident, caused Prime Minister Shinzo Abe to interrupt debate in parliament.
“In waters off Hyogo [prefecture], a tanker has exploded and is currently in flames,” he told lawmakers.
Television footage shot from helicopters showed thick columns of black smoke billowing from the stricken tanker as water jets doused it.
Coastguard officials said they had raced to the scene after hearing that the Shoko-Maru had exploded.
They said seven of the eight crew had been rescued, adding four of them had already been rushed to hospital, while three others were still on the ship in the care of first responders.
The Mainichi newspaper reported that the four sent to hospital were severely burned.
Television footage showed the approximately 80-metre ship listing heavily as at least two jets doused the badly-charred centre of the vessel.
Himeji port is one of a number that sit along the Inland Seto Sea coast, where there are numerous pockets of heavy industry.
The city itself is a popular tourist destination, and is home to one of Japan’s finest feudal castles.