A cargo ship carrying 21 people and hundreds of new cars was anchored off Sussex after a blaze ripped through its hold.

Explosions were heard on the 29,000-ton Oriental Highway after fire broke out yesterday morning, while it was 15 miles off Eastbourne.

Nine marine firefighters were airlifted from Newhaven by the coastguard helicopter based in Lee-on-Solent, Hampshire.

The firefighters were winched on to the anchored ship, which was carrying more than 480 Volkswagen and Audi A3 and A4 cars from Germany to Portugal.

The Bulgarian and Filipino crew used on-board firefighting equipment to flood the decks with CO2 foam to starve the hold of oxygen.

Another vessel, the Sand Serin, had drawn alongside the Oriental Highway in case the 21-strong crew needed to be evacuated.

However, the crew stayed in their cabins as firefighters spent more than four hours tackling and investigating the fire on deck seven of the ship's starboard side.

Firefighters contained the blaze to the hold, which was extensively smoke and fire damaged. About 30 cars were destroyed.

An inquiry into the fire's cause was under way last night, with one theory that it was sparked by a car's electrics.

RNLI lifeboats from Eastbourne and Hastings and the coastguard emergency tug pumped water on to ship's hold as it blistered under the heat.

Fears of pollution were raised as the ship contained 1,290 tons of oil and diesel.

However, Maritime and Coastguard Agency officials said no oil or diesel had leaked.

Frank Davis, assistant divisional officer for East Sussex Fire Brigade, said: "It's extremely difficult to fight fires at sea.

"In effect you are fighting a fire in a tin box, which is extremely dangerous and uses up an incredible amount of resources.

"Had the fire not been controlled in the early stages then it would have spread through each partition and would have been extremely difficult to stop.

"There's no doubt this had the potential to be very serious."

The vessel was last night anchored nine miles off Eastbourne. It was hoped it would carry on to Portugal following inspections.

The Eastbourne and Hastings lifeboats remained on stand-by until 4.30pm amid fears the fire could begin again.

David Osler, of Lloyd's List database of world ships, said the ship was owned by a unit of the Kawasaki Group called K Line, one of the world's largest car carriers.

It was transporting 483 cars but has a capacity to carry more than 3,000 vehicles .

Built in 1980, the vessel has had a very good safety record with no reports of being detained by port authorities.