The Indonesian navy has claimed a crude leak and subsequent fatal fire last month was caused by a bulker's anchor rupturing a pipeline.
The 82,000-dwt Ever Judger (built 2014) was damaged in the blaze on 31 March at Balikpapan.
Five fishermen were killed in the incident, which was possibly caused by one of their discarded cigarettes, or by workers trying to burn the oil away.
State producer Pertamina admitted the spill had come from one of its pipelines in the bay.
AFP cited Harjo Susmoro, head of the Indonesian navy's oceanography and hydrography centre, as saying: "We suspect the undersea pipe rupture was caused by the ship's anchor."
The navy claimed Ever Judger was the only cargo vessel in the area at the time of the accident.
Divers found a nearly 500m-long gash torn into the seabed that resembles the vessel's anchor, investigators said, according to AFP.
No charges
No charges have been laid and the investigation is ongoing.
The owner and manager of Ever Judger, Fleet Management Limited and Ever Judger (Holdings), told TradeWinds on Thursday that the ship had arrived in Balikpapan Bay on the night of 30 March under local pilotage.
"Managers and owners of the Ever Judger continue to cooperate fully with the investigation into the incident and oil spill emanating from the Pertamina pipeline in Balikpapan and await the outcome of the official investigation before commenting further," they added.
"Our thoughts and condolences go out to families who lost their loved ones in the tragic fire that followed the spill.
"As previously stated, if the official investigation identifies the vessel as being implicated in the incident, then owners and managers will meet their responsibilities in line with established international protocols.”
