The bulk carrier MV Wakashio that ran aground off Mauritius in late July has now split in two.
NHK World-Japan reported that Mitsui O.S.K. Lines had confirmed the Wakashio had broken apart on Saturday.
The firm said nearly all the 3,000 tons of bunker oil remaining onboard had already been recovered.
Mitsui O.S.K. Lines believes some 1,000 tons of heavy oil leaked from a cracked fuel tank into the sea after the incident and only around half of it has been recovered so far.
Work is continuing with the authorities of Mauritius and Japan to resolve the situation together with the owner of the ship.
The local environment, which includes coral reefs and waterfowl is in danger from the spillage.