The 39,910-ton vessel, the “Crimson Polaris”, was carrying wood chips when it ran aground Wednesday morning in the port of Hachinohe.
He managed to free himself, but due to bad weather he was unable to move far and ended up anchoring about 4 kilometers (2.4 miles) from the harbor.
The ship, which was at the end of a trip from Thailand, split into two early Thursday, the coast guard said.
An oil slick 5.1 kilometers long and about 1 kilometer wide was visible later that day, but containment measures were being taken by patrol boats.
Both parts of the ship have not moved and are closely watched by patrol boats, and by late afternoon there had been no apparent major changes in her situation, a Guard spokesman said. coastal.