British coastguards are hoping to remove 3,500 tonnes of oil from a ship beached off the Devon coast.
Two hundred tonnes of oil has already leaked out of the MSC Napoli.
Salvage teams had hoped to secure the ship and prevent so much oil leaking into the sea along the World Heritage Site coastline, but their efforts have been hampered by gale force weather conditions.
There is now an eight-kilometre slick of oil on the water's surface.
The Napoliwas deliberately run aground near Sidmouth, east Devon, after it was damaged during a storm on Thursday.
The 62,000-tonne ship is also carrying 2,400 containers, some of which contain potentially dangerous chemicals. At least 200 have gone overboard, three of which are carrying dangerous materials such as battery acid and perfume.
The ship contains 3,500 tonnes of heavy fuel oil, but a spokesman for the Maritime and Coastguard Agency (MCA) said they are confident it is contained in tanks within the ship that have not split.
There is a salvage team on board the Napoli, and a team of divers are being flown in to join them. They expect to start pumping out the remaining oil, and recovery teams have been mobilised to collect the debris from the beaches.