Oil is leaking from the wreck of the 13,800-dwt bulker Ultra Galaxy (built 2008), which listed in bad weather off the coast of South Africa.
Aerial photographs taken by the South African Maritime Authority show the wreck has split in two and capsized further. Large parts are now underwater.
The vessel was en route from Europe to Dar es Salaam, Tanzania, with a cargo of fertiliser when it developed a list in poor weather and the crew was forced to abandon ship.
The authorities suggested the list may have been caused by the liquefaction of the ammonium nitrate cargo.
It grounded on 9 July off the West coast of South Africa where salvage efforts have been constantly hampered by bad weather.
The authority said the oil is drifting and has reached some beaches. It also said it was coordinating with local authorities to manage the environmental impact of the spill.
Additional volunteers are being drafted in to help clean up the spill.
