Coastguards say there are 158 containers with hazardous chemical substances on board, but most of them are in the ship's hold.
Coastguards say there are 168 containers with hazardous chemical substances on board, but most of them are in the ship's hold.
Mark Clark, of the Maritime and Coastguard Agency (MCA), told BBC News: "She could capsize at any moment, but there's always been a risk that the ship would twist and capsize.
Mark Clark, of the Maritime and Coastguard Agency (MCA), told BBC News: "She could capsize at any moment, but there's always been a risk that the ship would twist and capsize.
"She is currently listing at 35 degrees, which is a very heavy list, but she is not going any further at the moment."
"She is currently listing at 35 degrees, which is a very heavy list, but she is not going any further at the moment."
A capsize raises fears of an environmental disaster, but Chris Lawson of the Environment Agency earlier told BBC News there was "very little risk" of the chemicals leaking.
The 26 crew were airlifted to safety after it was holed off Lizard Point, Cornwall, in the English Channel on Thursday.
The rescue team has been using high tides to edge the Napoli closer to shelter whilst weighing it down by pumping in sea water as a ballast.
Coastguards said the priority was to safeguard approximately 3,000 tonnes of fuel on board and pump it out of the vessel over the next two to three days.
Oil slick
The ship, which is carrying almost 2,400 containers, has been surrounded by a 1km (0.6 mile) oil-protection boom to protect the sea from any possible pollution.
The Napoli was run aground on Saturday following "serious structural failure".
The stern of the ship is awash after a crack in the hull threatened to leave the ship broken in two.
How crew were rescuedClick here for map It is now listing heavily to starboard and eyewitnesses have spoken of hearing the noise of containers shifting on deck.
The drifting vessel was being towed to Portland Harbour in Dorset for a salvage operation, but the MCA decided to beach it in Lyme Bay, near Sidmouth, instead, following the structural failure.
Coastguards are out looking for the missing 40ft long containers, which include one containing hundreds of thousands of pounds worth of BMW motorbikes.
An MCA spokesman said the environmental sensitivities in the Lyme Bay area had been fully assessed before the decision to run it into the ground.
"The oils will be the first priority, the ship's bunkers, fuel oil, and then the containers which are considered most hazardous first," said the MCA's Paul Coley.
The 275m (900ft), 62,000-tonne Napoli is registered in London and owned by the Swiss Mediterranean Shipping Company.
It was last inspected by the MCA in May 2005 when officials said it met safety standards.
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