It said the vessel was registered in Mozambique, and that it was in the process of contacting Mozambican authorities to inform them about the incident.
KwaZulu-Natal EMS responded to the fire, which started at about 2.30pm on Thursday. Three people were taken to hospital, but six others were found dead on the ship on Friday morning.
Firefighters brought the fire under control around 6pm on Thursday, but the vessel was not deemed safe to board.
Rescue Care spokesperson Garrith Jamieson said the six deceased were found on Friday morning at around 2am.
There was a Mozambican flag on board the ship, with pictures from emergency services showing that half the flag had been burnt.