Pounding spring tide waves whipped up by a westerly wind have broken the back of the TMP Sagittarius, stranded off Leaches Bay in East London, the Smit Marine salvage company said on Wednesday.
Spokesperson Dave Main said that, as yet, there was no danger of pollution to the coastline. The ship's gas oil is stored in the engine room behind the break and was secure at present.
"Her back broke on Tuesday because she has taken too much strain," Main said.
National Port Authority spokesperson Terry Taylor added that the "deck plating has cracked right across the sides of the hull (bottom) on both the port (left) and starboard (right) sides".
The ship has constantly been pounded by huge waves since it ran aground on a rocky outcrop last Thursday night. Main said he could not say if the ship would break further, but that it was taking in water from the swell.
He said the salvage team would not be able to burn any of the ship's fuel - marine gas oil - until the weather improved.
"The oil is not heavy and about 50 tons needs to be burnt," he said, adding "this can be done at a couple of tons per hour".
To burn the gas oil, it has to be pumped up to a tank on deck with the water drained from it. The gas oil is then fed into the boiler and burnt. - Sapa